qemu-ga: Plug file descriptor leak on ga_open_pidfile() error path Spotted by Coverity. Also document why we keep it open on success. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com> Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com> Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>