Btrfs: correctly set profile flags on seqlock retry

If we had to retry on the profiles seqlock (due to a concurrent write), we
would set bits on the input flags that corresponded both to the current
profile and to previous values of the profile.

Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: Chris Mason <clm@fb.com>