block: vservices: fix client and server to work for UFS

Fix block vservice client and server to support UFS storage,
which requires a minimum block size of 4096 bytes.

CRs-Fixed: 2288669

Change-Id: I3846a86925efbfbf8840e99226962de6d09b3b70
Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Minming Qi <mqi@codeaurora.org>
Signed-off-by: zhaochen <zhaochen@codeaurora.org>