vos: Interpret VLOP_* lock flags

vos: Interpret VLOP_* lock flags

When a volume is locked in the VLDB, we are given flags for the reason
why the lock was set. Make vos interpret and output this reason.

This adds output to any vos command that previously printed that a
volume was LOCKED. It now outputs, for example,

    Volume is currently LOCKED
    Volume is locked for a delete/misc operation

Change-Id: Ie3a6f804a3e3a551840975c3689b24d3916891df
Reviewed-on: http://gerrit.openafs.org/2235
Tested-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Jason Edgecombe <jason@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>