4086 readonly option for lofiadm(1m)
Reviewed by: Garrett D'Amore <garrett@damore.org>
Reviewed by: Yuri Pankov <yuri.pankov@nexenta.com>
Approved by: Robert Mustacchi <rm@joyent.com>
	[illumos-gate merge]

commit cd69fabe0332d2cf0e51b2cb6597286e0abcf6be
    4086 readonly option for lofiadm(1m)

	Conflict: usr/src/cmd/lofiadm/main.c (OS-20)