In camperiphdone(), make sure we check for fatal errors and bail out

In camperiphdone(), make sure we check for fatal errors and bail out
instead of retrying them blindly.

This should fix some of the problems people have been having with cdrom
drives taking a long time to probe.  This should also eliminate the need
for the initial TUR in cdsize().

cam_periph.c:	Don't keep retrying if the error we get back is a fatal
		error.  This should help us detect the transition from
		"Logical unit not ready, cause not reportable" to "Medium
		not present" in the "TUR many" handler.  (The TUR many
		handler gets triggered for Logical unit not ready, cause
		not reportable errors.)

scsi_cd.c:	Remove the initial test unit ready in cdsize().  Hopefully
		it isn't necessary after the above change.

Submitted by:	gibbs (mostly)
Tested by:	peter
MFC After:	2 weeks