md/raid1: Fix data corruption for degraded array with slow disk

In the Linux kernel, the following vulnerability has been resolved:

md/raid1: Fix data corruption for degraded array with slow disk

read_balance() will avoid reading from slow disks as much as possible,
however, if valid data only lands in slow disks, and a new normal disk
is still in recovery, unrecovered data can be read:

raid1_read_request
read_balance
raid1_should_read_first
-> return false
choose_best_rdev
-> normal disk is not recovered, return -1
choose_bb_rdev
-> missing the checking of recovery, return the normal disk
-> read unrecovered data

Root cause is that the checking of recovery is missing in
choose_bb_rdev(). Hence add such checking to fix the problem.

Also fix similar problem in choose_slow_rdev().