Fix multipath bug in vdev_id caused by inconsistent field numbering.

This is an update to the previous fix, with correct indentation,
and using only awk, avoiding spawning an additional sed process.

The bug is caused by multipath output like this:
35000c50056bd77a7 dm-15 HP,MB3000FCWDH
size=2.7T features='0' hwhandler='0' wp=rw
|-+- policy='round-robin 0' prio=0 status=active
| `- 2:0:16:0 sdq  65:0    active undef running
`-+- policy='round-robin 0' prio=0 status=enabled
  `- 4:0:52:0 sdfp 130:176 active undef running
Note that the pipe symbols mean that the field numbering is different
between the sdq and sdfp lines.  The fix edits out the pipe symbols.