Revision 330522

MFC r326401:

Fix assertion when ZFS fails to open certain devices

"panic: vdev_geom_close_locked: cp->private is NULL"
This panic will result if ZFS fails to open a device due to either of the
following reasons:

1) The device's sector size is greater than 8KB.
2) ZFS wants to open the device RW, but it can't be opened for writing.

The solution is to change the initialization order to ensure that the
assertion will be satisfied.

PR:		221066
Reported by:	David NewHamlet <wheelcomplex@gmail.com>
Reviewed by:	avg
Sponsored by:	Spectra Logic Corp
Differential Revision:	https://reviews.freebsd.org/D13278