Run the libexif-testsuite tests in parallel now that they can be.

.travis.yml

@@ -151,7 +151,7 @@ script:
   - if [ "$CONFIG" = "clang6" ] ; then CFLAGS='-Wall -Wextra -O3'; export CC=clang-6.0; fi
   - if [ "$CONFIG" = "gcc8" ] ; then CFLAGS='-Wall -Wextra -O3'; export export CC=gcc-8; fi
   - if [ "$CONFIG" = "sanitize" ] ; then CFLAGS='-g -Wall -Wextra -fsanitize=address -fsanitize=undefined'; export CC=clang-6.0; CONFIGURE_OPTS="POPT_CFLAGS=-I${HOME}/popt/include POPT_LIBS=-lpopt LDFLAGS=-L${HOME}/popt/lib"; fi
-  - if [ "$CONFIG" = "coverage" ] ; then cd "$HOME"/libexif-testsuite; CFLAGS=--coverage; CONFIGURE_OPTS='LDFLAGS=--coverage'; export MAKEFLAGS='-j 1'; fi
+  - if [ "$CONFIG" = "coverage" ] ; then cd "$HOME"/libexif-testsuite; CFLAGS=--coverage; CONFIGURE_OPTS='LDFLAGS=--coverage'; fi
   - ./configure --prefix="${HOME}" CFLAGS="$CFLAGS" PKG_CONFIG_PATH="${HOME}/lib/pkgconfig" $CONFIGURE_OPTS || { tail -300 config.log; false; }
   - make
   - make check || { tail -300 test*/test-suite.log; false; }