subrepo: ensure "close()" execution at the end of "_readstorehashcache()"

Before this patch, "close()" for the file object opened in
"_readstorehashcache()" may not be executed, if unexpected exception
is raised, because it isn't executed in "finally" clause.

This patch ensures "close()" execution at the end of
"_readstorehashcache()" by moving it into "finally" clause.

mercurial/subrepo.py

@@ -576,7 +576,9 class hgsubrepo(abstractsubrepo):
         if not os.path.exists(cachefile):
             return ''
         fd = open(cachefile, 'r')
+        try:
         pullstate = fd.readlines()
+        finally:
         fd.close()
         return pullstate