Timeout devstack/tempest internally

Abort the run of the gate script within the wrap script
after a specified time (60 minutes by default).  The wrap
script will be able to proceed to copy log files as usual
in case of a timeout.

Remove xtrace option that slipped in during earlier
devstack-gate testing.

Change-Id: I000fae1365534b204ab27f2014ba64eabafc7584
Merge "Timeout devstack/tempest internally"