[ci] Run functional tests using bitcoin-qt in one Travis job

As noted in bitcoin#12843, we're currently
missing bugs unique to bitcoin-qt during the Travis build because the
functional test framework only uses bitcoind (and not bitcoin-qt).

Run a single Travis job under xvfb for framebuffer virtualization and using
bitcoin-qt as the binary. Remove outdated NEED_XVFB Travis configuration.

.travis.yml

@@ -24,6 +24,7 @@ env:
     - SDK_URL=https://bitcoincore.org/depends-sources/sdks
     - WINEDEBUG=fixme-all
     - DOCKER_PACKAGES="build-essential libtool autotools-dev automake pkg-config bsdmainutils curl git ca-certificates ccache"
+    - FUNCTIONAL_TEST_CMD="test/functional/test_runner.py --combinedlogslen=4000 --coverage --quiet --failfast"
   matrix:
 # ARM
     - HOST=arm-linux-gnueabihf PACKAGES="g++-arm-linux-gnueabihf" DEP_OPTS="NO_QT=1" GOAL="install" BITCOIN_CONFIG="--enable-glibc-back-compat --enable-reduce-exports"
@@ -36,7 +37,7 @@ env:
 # x86_64 Linux (uses qt5 dev package instead of depends Qt to speed up build and avoid timeout)
     - HOST=x86_64-unknown-linux-gnu PACKAGES="python3-zmq qtbase5-dev qttools5-dev-tools protobuf-compiler libdbus-1-dev libharfbuzz-dev libprotobuf-dev" DEP_OPTS="NO_QT=1 NO_UPNP=1 DEBUG=1 ALLOW_HOST_PACKAGES=1" RUN_TESTS=true GOAL="install" BITCOIN_CONFIG="--enable-zmq --with-gui=qt5 --enable-glibc-back-compat --enable-reduce-exports CPPFLAGS=-DDEBUG_LOCKORDER"
 # Qt4 & system libs
-    - HOST=x86_64-unknown-linux-gnu PACKAGES="python3-zmq qt4-dev-tools libssl1.0-dev libevent-dev bsdmainutils libboost-system-dev libboost-filesystem-dev libboost-chrono-dev libboost-program-options-dev libboost-test-dev libboost-thread-dev libdb5.3++-dev libminiupnpc-dev libzmq3-dev libprotobuf-dev protobuf-compiler libqrencode-dev xvfb libqt4-dev" NO_DEPENDS=1 NEED_XVFB=1 RUN_TESTS=true GOAL="install" BITCOIN_CONFIG="--enable-zmq --with-incompatible-bdb --enable-glibc-back-compat --enable-reduce-exports --with-gui=qt4 CPPFLAGS=-DDEBUG_LOCKORDER" DISPLAY=:99.0
+    - HOST=x86_64-unknown-linux-gnu PACKAGES="python3-zmq qt4-dev-tools libssl1.0-dev libevent-dev bsdmainutils libboost-system-dev libboost-filesystem-dev libboost-chrono-dev libboost-program-options-dev libboost-test-dev libboost-thread-dev libdb5.3++-dev libminiupnpc-dev libzmq3-dev libprotobuf-dev protobuf-compiler libqrencode-dev xvfb libqt4-dev" NO_DEPENDS=1 RUN_TESTS=true RUN_TESTS_WITH_QT=true GOAL="install" BITCOIN_CONFIG="--enable-zmq --with-incompatible-bdb --enable-glibc-back-compat --enable-reduce-exports --with-gui=qt4 CPPFLAGS=-DDEBUG_LOCKORDER" DISPLAY=:99.0
 # x86_64 Linux, No wallet
     - HOST=x86_64-unknown-linux-gnu PACKAGES="python3" DEP_OPTS="NO_WALLET=1" RUN_TESTS=true GOAL="install" BITCOIN_CONFIG="--enable-glibc-back-compat --enable-reduce-exports"
 # Cross-Mac
@@ -59,7 +60,12 @@ before_script:
     - if [[ $HOST = *-mingw32 ]]; then DOCKER_EXEC update-alternatives --set $HOST-g++ \$\(which $HOST-g++-posix\); fi
     - if [ -z "$NO_DEPENDS" ]; then DOCKER_EXEC CONFIG_SHELL= make $MAKEJOBS -C depends HOST=$HOST $DEP_OPTS; fi
     # Start xvfb if needed, as documented at https://docs.travis-ci.com/user/gui-and-headless-browsers/#Using-xvfb-to-Run-Tests-That-Require-a-GUI
-    - if [ "$NEED_XVFB" = 1 ]; then DOCKER_EXEC /sbin/start-stop-daemon --start --pidfile /tmp/custom_xvfb_99.pid --make-pidfile --background --exec /usr/bin/Xvfb -- :99 -ac; fi
+    - |
+      if [ "$RUN_TESTS_WITH_QT" = "true" ]; then
+        # Start xvfb per an issue describing difficulty with Travis and Ubuntu Trusty:
+        # https://github.com/travis-ci/travis-ci/issues/8262#issuecomment-323601110
+        DOCKER_EXEC /sbin/start-stop-daemon --start --pidfile /tmp/custom_xvfb_99.pid --make-pidfile --background --exec /usr/bin/Xvfb -- :99 -ac -screen 0 1280x1024x24;
+      fi
 script:
     - export TRAVIS_COMMIT_LOG=`git log --format=fuller -1`
     - OUTDIR=$BASE_OUTDIR/$TRAVIS_PULL_REQUEST/$TRAVIS_JOB_NUMBER-$HOST
@@ -74,7 +80,11 @@ script:
     - DOCKER_EXEC make $MAKEJOBS $GOAL || ( echo "Build failure. Verbose build follows." && DOCKER_EXEC make $GOAL V=1 ; false )
     - if [ "$RUN_TESTS" = "true" ]; then DOCKER_EXEC LD_LIBRARY_PATH=$TRAVIS_BUILD_DIR/depends/$HOST/lib make $MAKEJOBS check VERBOSE=1; fi
     - if [ "$TRAVIS_EVENT_TYPE" = "cron" ]; then extended="--extended --exclude feature_pruning,feature_dbcrash"; fi
-    - if [ "$RUN_TESTS" = "true" ]; then DOCKER_EXEC test/functional/test_runner.py --combinedlogslen=4000 --coverage --quiet --failfast ${extended}; fi
+    - if [ "$RUN_TESTS_WITH_QT" = "true" ]; then
+          DOCKER_EXEC BITCOIND=$(DOCKER_EXEC find . -name 'bitcoin-qt' -executable) $FUNCTIONAL_TEST_CMD ${extended};
+        elif [ "$RUN_TESTS" = "true" ]; then
+          DOCKER_EXEC $FUNCTIONAL_TEST_CMD ${extended};
+        fi
 after_script:
     - echo $TRAVIS_COMMIT_RANGE
     - echo $TRAVIS_COMMIT_LOG