Btrfs: Print key type in decimal everywhere

This is confusing, sometimes the key type is printed in hex (without
a leading "0x" which makes things even more complicated), sometimes
in decimal...
Change it to be in decimal everywhere.

Signed-off-by: Stefan Behrens <sbehrens@giantdisaster.de>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>