Use 'travis_wait' to prevent Travis CI from aborting builds

Builds use the '-q' flag to suppress most output due to a limit of 4MB
of logs on Travis CI. However, Travis will also abort builds that
don't generate any output for 10 minutes. Thus we also use the
'travis_wait' function to make sure builds aren't aborted for up to
30 minutes.

Fixes gh-6621
Closes gh-6623

.travis.yml

@@ -6,7 +6,5 @@ services:
   - redis
 sudo: false
 install: true
-before_script:
+before_script: travis_wait 30 ./mvnw install -q -U -DskipTests=true -Dmaven.test.redirectTestOutputToFile=true
-- ./mvnw install -q -U -DskipTests=true -Dmaven.test.redirectTestOutputToFile=true || true
+script: ./mvnw install -q -nsu -Dmaven.test.redirectTestOutputToFile=true -P '!integration'
-- ./mvnw install -q -U -DskipTests=true -Dmaven.test.redirectTestOutputToFile=true
-script: ./mvnw install -q -nsu -Dmaven.test.redirectTestOutputToFile=true -P '!integration'