A very basic path selector: round-robin.

It uses in turn each path that has not been disabled.

By default, it instructs core multipath to use each path it supplies for 1000
bios, but a different repeat_count can be set against any path to provide
primitive load-balancing across unequal paths.
Signed-Off-By: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>