Wait for disk when attaching volumes

It might take some time to discover new device in guest OS.
This patch adds waiter for device after we attached volume.

Change-Id: I1d35f6ed94fcd152a63f61ef6e073bc7fff40daa
Related-Prod: PROD-21942
(cherry picked from commit 4dc8f4e0e45a3798a3aa2cac37651acd014c4f28)
1 file changed