Use pg initialization script from Travis

ci/travis/linux/before_script.sh

@@ -1,5 +1,4 @@
 printf "[qgis_test]\nhost=localhost\ndbname=qgis_test\nuser=postgres" > ~/.pg_service.conf
-psql -c 'CREATE DATABASE qgis_test;' -U postgres
-psql -f $TRAVIS_BUILD_DIR/tests/testdata/provider/testdata_pg.sql -U postgres -d qgis_test
-psql -f $TRAVIS_BUILD_DIR/tests/testdata/provider/testdata_pg_reltests.sql -U postgres -d qgis_test
-psql -f $TRAVIS_BUILD_DIR/tests/testdata/provider/testdata_pg_vectorjoin.sql -U postgres -d qgis_test
+
+export PGUSER=postgres
+$TRAVIS_BUILD_DIR/tests/testdata/provider/testdata_pg.sh