Merge branch 'stable-3.1'
Fix log statement formatting
GerritRestApi: Use UTF_8 from StandardCharsets instead of Guava
Fix NPE in PushResultProcessing
Fix start --wait to track in-flight collisions and to not fail
Improve URLmatching to match real Urls
Convert PushResultProcessing to an interface
ReplicationQueue: Revert back from Flogger to slf4j logging
The change "Revert back from Flogger to slf4j logging" is omitted from
this merge. Since change I0d18f8931 which was submitted earlier on the
master branch, Flogger logging is fixed.