bsdacct: fix uid/gid misreporting

commit d8e180dcd5bbbab9cd3ff2e779efcf70692ef541 "bsdacct: switch
credentials for writing to the accounting file" introduced credential
switching during final acct data collecting.  However, uid/gid pair
continued to be collected from current which became credentials of who
created acct file, not who exits.

Addresses http://bugzilla.kernel.org/show_bug.cgi?id=14676

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Reported-by: Juho K. Juopperi <jkj@kapsi.fi>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: David Howells <dhowells@redhat.com>
Reviewed-by: Michal Schmidt <mschmidt@redhat.com>
Cc: James Morris <jmorris@namei.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>