glusterd: really get the inode size for a brick

The device to get the inode size from does not get passed to the tool
(tune2fs, xfs_info or the like) that is called. This is probably just an
oversight. While correcting this, cleanup some bits of the function too.

Change-Id: Ida45852cba061631fb304bc7dd5286df1a808010
BUG: 1130462
Signed-off-by: Niels de Vos <ndevos@redhat.com>
Reviewed-on: http://review.gluster.org/8492
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>
Reviewed-by: Krishnan Parthasarathi <kparthas@redhat.com>
Tested-by: Krishnan Parthasarathi <kparthas@redhat.com>