LU-4887 lfsck: run all LFSCK scan types by default

LU-4887 lfsck: run all LFSCK scan types by default

When running "lctl lfsck_start" run all available scan types by
default (scrub, layout, and namespace currently) if none is given.
If '-t' is given, run only the specified scan types. 'scrub' is
always run.

Rename the lfsck_type constants to use a LFSCK_TYPE_ prefix to be
more descriptive.  Add LFSCK_TYPE_ constants to wirecheck.
Add ltn_ prefix to lfsck_type_name structure.

Print the available types from the lfsck_types_names[] array in
the help message instead of hard-coding them in the help message.

Don't return an error if "lctl lfsck_stop" is used when stopped.

Fix up lfsck_namespace /proc stats to use more descriptive names.

Signed-off-by: Fan Yong <fan.yong@intel.com>
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: I106483ade0bf07c2920dd95a263acdbe4e500c1e
Reviewed-on: http://review.whamcloud.com/10278
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Nunez <james.a.nunez@intel.com>