afs: Fix manually set volume location server list

When a cell with a volume location server list is added manually by
echoing the details into /proc/net/afs/cells, a record is added but the
flag saying it has been looked up isn't set.

This causes the VL server rotation code to wait forever, with the top of
/proc/pid/stack looking like:

	afs_select_vlserver+0x3a6/0x6f3
	afs_vl_lookup_vldb+0x4b/0x92
	afs_create_volume+0x25/0x1b9
	...

with the thread stuck in afs_start_vl_iteration() waiting for
AFS_CELL_FL_NO_LOOKUP_YET to be cleared.

Fix this by clearing AFS_CELL_FL_NO_LOOKUP_YET when setting up a record
if that record's details were supplied manually.

Fixes: 0a5143f2

 ("afs: Implement VL server rotation")
Reported-by: Dave Botsch <dwb7@cornell.edu>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>