Fix multipath bug in vdev_id caused by inconsistent field numbering

Fix multipath bug in vdev_id caused by inconsistent field numbering

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.

Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1692