Bug 1608: Make ActorContext ASK_DURATION configurable

Made the duration timeout for akka ask operations configurable via the
config system.

Also removed the explicit passing of the duration timeout to
ActorContext#exeucte* methods since all calls previously passed the
static ActorContext.ASK_DURATION.

Change-Id: Ic54e65d8d444110294048348472d1d8d56f0fd44
Signed-off-by: tpantelis <tpanteli@brocade.com>
Merge "Bug 1608: Make ActorContext ASK_DURATION configurable"