re-add $wgWBClientSettings["siteGlobalID"] = "enwiki" for travis setup

this is in TestSites and avoids various notices like
"Notice: Cannot find site its_a_mw in sites table" that
occur via hooks.

Change-Id: I45e01863574a9f9d994c013cc1cf92391385e349
Merge "re-add $wgWBClientSettings["siteGlobalID"] = "enwiki" for travis setup"