[BrowserTest] create a Template at run time

For the case of a bare wiki, make a page Template:Seleniumtest
so that something will show up when typing into the lookahead
box in the Template inspector

Note that it may take a small amount of time for the new
Template to be available to VE. If this test fails on
the first run in a bare wiki, it should pass on the
second run ,once the Template is indexed by the
search back end.
Change-Id: I70d1ff39c2fd01bb0aeee89d3c090d372b427f5b
Merge "[BrowserTest] create a Template at run time"