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.