btrfs: Separate scrub_blocked_if_needed() to scrub_pause_on/off()
btrfs: Separate scrub_blocked_if_needed() to scrub_pause_on/off()

It can reduce current duplicated code which is similar to
scrub_blocked_if_needed() but can not call it because little
different.
It also used by my next patch which is in same case.

Signed-off-by: Zhao Lei <aacdd228f50c574b28b524b23f12fb9d52d6e0e3@cn.fujitsu.com>
Signed-off-by: Chris Mason <e2e8c5702d8ed5f565988a1cf5bb35c9ce199e5e@fb.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs