[GFS2] Audit printk and kmalloc

All printk calls now have KERN_ set where required and a couple of
kmalloc(), memset(.., 0, ...) calls changed to kzalloc().

This is in response to comments from:
Pekka Enberg <penberg@cs.helsinki.fi> and
Eric Sesterhenn <snakebyte@gmx.de>

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>