tests: merge 'test-push-hook-lock.t' into 'test-push.t'
That test file is very small and is merge with the new 'test-push.t'. No logic
is changed.
We don't register this as a copy because is actually a "ypoc" merging two file
together without replacing the destination and Mercurial cannot express that.
ERROR: FIXME: This is a known failure of filelog.size for data starting with \1\n
OK.