LU-8055 ldev: Introduced role filtering

LU-8055 ldev: Introduced role filtering

Output can now be filtered by using -R <role>
or --role <role> as command line parameters,
where role is a string such as "mdt", "ost",
or "mgs".

Also removed MGT as a possible node type
in ldev.conf.

Test-Parameters: trivial testlist=conf-sanity
Signed-off-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Change-Id: I488ac702edf0cc7c08020b289dcba040706181b4
Reviewed-on: http://review.whamcloud.com/20041
Reviewed-by: Olaf Faaland-LLNL <faaland1@llnl.gov>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Christopher J. Morrone <morrone2@llnl.gov>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>