LU-12935 obdclass: fix import connect flag printing

LU-12935 obdclass: fix import connect flag printing

The obd_connect_names[] array holds strings for the OBD_CONNECT_*
and obd_CONNECT2_* flag names.  It is positional, so every flag
bit needs a corresponding field in the array.

The "async_discard" feature was backported to b2_12, but the two
earlier features "pcc" and (now removed) "plain_layout" were not
backported.  Add in strings for those features, and fill in some
earlier "unknown" flag names as well

Fixes: e5810126b3fb ("LU-11359 mdt: fix mdt_dom_discard_data() timeouts")
Test-Parameters: trivial
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I883d236262805361be3f48c533d781878f9494fa
Reviewed-on: https://review.whamcloud.com/36881
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Mike Pershin <mpershin@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.super@gmail.com>
Reviewed-by: Shaun Tancheff <stancheff@cray.com>
Reviewed-by: Stephan Thiell <sthiell@stanford.edu>
Reviewed-by: Oleg Drokin <green@whamcloud.com>