Remove do_mkdir and simplify mkdirs

Change-Id: I2e629533bceafb341ced5b1b3f2436448293e03f
Signed-off-by: Luis Pabon <lpabon@redhat.com>
Reviewed-on: http://review.gluster.org/5304
Reviewed-by: Peter Portante <pportant@redhat.com>
Tested-by: Peter Portante <pportant@redhat.com>