Update attach logic in VolumeEncryptionTest

Pick the same logic as volume attach tests have, when after
volume attach server is rebooted to make sure guest OS
recognize new device.

Change-Id: I92098c7d994dc7d85643da29380866a805f4e869
Related-Prod: PRODX-360
(cherry picked from commit 40bbd545a59328363c9ca8785d0d1eaed1eb8aed)
(cherry picked from commit c17ff148134712b8c8606608ef7d7abc789605ce)
1 file changed