Check subnet CIDR is only IP version 4

Change-Id: Iad1edef2c1e3ff734f7fad0a01e2edffd763d72e
(cherry picked from commit 7dacf043d5b13b66acbd3fc00b36b0cb359c9cb4)
Merge "Check subnet CIDR is only IP version 4" into R1.10