md: Fix bug in error handling during raid1 repair.

md: Fix bug in error handling during raid1 repair.

If raid1/repair (which reads all block and fixes any differences
it finds) hits a read error, it doesn't reset the bio for writing
before writing correct data back, so the read error isn't fixed,
and the device probably gets a zero-length write which it might
complain about.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>