xlock: Rename Noone to XLOCK_NOONE
xlock: Add XLOCK_XSEGTOOL owner
xseg: Use the newly introduced XLOCK_UNKNOWN_OWNER

Change all xlock_acquire occurrences where a dummy owner value was used, to the
new XLOCK_UNKNOWN_OWNER value.
xseg-tool: Use the reserved XLOCK_XSEGTOOL owner
xseg-tool: Remove unused port args from failport