mercurial.el: ignore errors on hg-after-save-hook()
Don't signal an error even if running hg command fails. Otherwise,
succeeding hooks won't be called.
adding dir/bar
adding foo
dir/bar
foo
adding dir/bar_2
adding foo_2
dir/bar_2
foo_2
adding a
adding c
adding b
adding d
removing a
removing c
recording removal of a as rename to b (100% similar)