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

@@ -576,8 +576,10 b' class hgsubrepo(abstractsubrepo):'
         if not os.path.exists(cachefile):
             return ''
         fd = open(cachefile, 'r')
-        pullstate = fd.readlines()
-        fd.close()
+        try:
+            pullstate = fd.readlines()
+        finally:
+            fd.close()
         return pullstate
 
     def _cachestorehash(self, remotepath):