ext4: really print the find_group_flex fallback warning only once

(cherry picked from commit 6b82f3cb)

Missing braces caused the warning to print more than once.

Signed-Off-By: Chuck Ebbert <cebbert@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>