Upgrade to Logback 1.1.9

Logback's internal executor service had a thread pool size of 2 which could be used up rather quickly, e.g. configuration scanning in addition to an active ServerSocketAppender. When both threads where permanently in use, compression could not proceed. To alleviate this problem, the thread pool size has been increased to 8. See issue LOGBACK-1238 for more details.

Fixed issue with FileAppender instances embedded within SiftingAppender reporting filename collisions after reaching timeout and subsequently restarted. This problem was reported in LOGBACK-1167 by Michael Edgar.

Fixed SizeAndTimeBasedFNATP deprecation warning emitted even the replacement, i.e. SizeAndTimeBasedRollingPolicy, is in use. See LOGBACK-1236. This issue was reported by Claudius Nicolae.

Added proper implementation for LobackValve.getScheduledExecutorService() method. The missing implementation manifested itself in the form of an UnsupportedOperationException thrown by LogbackValve. This problem is further described in LOGBACK-1181 reported by Andreas von Roepenack.