bitbake: lib/bb/fetch/hg: fix fetching from a mercurial repository

* without this fix, we get :
updating working directory
74 files updated, 0 files merged, 0 files removed, 0 files unresolved
abort: There is no Mercurial repository here (.hg not found)!

(Bitbake rev: 75ea005ac8fc05b2b3afca803d77a6b5f558efee)

Signed-off-by: Eric Bénard <eric@eukrea.com>
Tested-by: Frans Meulenbroeks <fransmeulenbroeks@gmail.com>
Signed-off-by: Chris Larson <chris_larson@mentor.com>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>

bitbake/lib/bb/fetch/hg.py

@@ -140,6 +140,7 @@ class Hg(Fetch):
         # Even when we clone (fetch), we still need to update as hg's clone
         # won't checkout the specified revision if its on a branch
         updatecmd = self._buildhgcommand(ud, d, "update")
+        os.chdir(ud.moddir)
         logger.debug(1, "Running %s", updatecmd)
         runfetchcmd(updatecmd, d)