CBQE-0: print exception in get_all_builds

Change-Id: I1208c639129c05d26d1c5212a640d97e52c47f91
Reviewed-on: http://review.couchbase.org/30380
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>