Add a timeout when joining the gluster upload thread.

Summary:
This will stop the gluster_util after 15 secs, if it is hanging.

Test Plan: run it.

Reviewers: lguo

CC:

Task ID: #

Blame Rev:
join 30 secs.
Bump the wal-e version to 2.9
bump the version to 2.11
Merge pull request #5 from DikangGu/v0.7.0insta2

Add a timeout when joining the gluster upload thread.