Make rejoin-stack.sh resume file logging if enabled

This patch ensures that screen will resume logging to files
after rejoin-stack.sh when SCREEN_LOGDIR is set.

Change-Id: I4c3eae0df7755b700dd8acf4bf14b7e383372ca3
Closes-bug: 1192568
Merge "Make rejoin-stack.sh resume file logging if enabled"