[maven-release-plugin] prepare release 1.6.11 #2516

Job	Run time
Build	3m 26s
test-brokerAcl	13m 36s
test-datastore	9m 27s
test-broker	13m 28s
test-connection	11m 24s
test-device	3m 47s
test-device-management	4m 6s
test-tag	3m 51s
test-account	7m 47s
test-jobEngineStartOfflineDevice	11m 12s
test-jobEngineStartOnlineDevice	10m 7s
test-jobEngineStepDefinitions	4m 14s
test-jobs	7m 57s
test-security	6m 7s
test-triggerService	6m 23s
test-user	10m 18s
build-javadoc	4m 30s
test-jobEngineRestartOfflineDevice	10m 31s
junit-tests	6m 24s
test-jobEngineRestartOnlineDevice	15m 30s
test-jobEngineRestartOnlineDeviceSecondPart	8m 37s
test-jobEngineServiceStop	7m 52s
	3h 0m 34s

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