Collect javelin2 log

As of Id5c0dfeaf8e7e9ed1d54f51c54e6e5c65b1361fa javelin will now log to
the file javelin.log collect this log for debugging.

Check for the files existence before attempting to collect to allow this
patch to land before the grenade patch lands.

Change-Id: I787c08506d9a4d12081b5b5b16d752d5147f8e72
Merge "Collect javelin2 log"