drbd: Fix the WO=drain implementation for multiple volumes
drbd: Fix the WO=drain implementation for multiple volumes

Wait until IO is drained in all volumes.

Signed-off-by: Philipp Reisner <35a55a4ac466b5abd81eb66f3f7d6a972dd0dc24@linbit.com>
Signed-off-by: Lars Ellenberg <31df9cacdc65c624cc60c2dcd22bbf92dc230e16@linbit.com>

KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs