eina: fix a possible race condition during eina_file_close.

eina: fix a possible race condition during eina_file_close.

The lock on the main hash was taken to late (after we took the decision
to remove the targeted Eina_File from the cache), this means it was possible
to get an Eina_File from the cache that was going to be removed. This patch
attempt to fix that potential race condition.

Hopefully should fix T461.