CBQE-1147 Offline upgrade for linux

Right now upgrade phase are not automated. Also, since the
test spec involve multiple cluster, wait for multiple vhosts
among workers implemented

Change-Id: I100c50babc087d65bc2f22bbaa1a8cd866877bcb
Reviewed-on: http://review.couchbase.org/25881
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Chisheng Hong <chisheng@couchbase.com>
Tested-by: Chisheng Hong <chisheng@couchbase.com>