Make NodeAvailabilityCache TTL configurable, increase default from 50 to 1000 millis.

The TTL defines, how long the availability (or inavailability) of a given memcached
node is cached (considered to be correct). If a request comes in after the TTL has
passed msm will "ping" the related memcached node to see if it's yet available (or
available again).
Make memcached client maxReconnectDelay configurable via sys prop "msm.maxReconnectDelay"

The maxReconnectDelay is specified in seconds.
Merge remote-tracking branch 'upstream/master' into statistics
setup statistic time unit with system property msm.statistics.timeunit
calc ping check stats