Avoid setting prefix length for 0.0.0.0 address

The ioctl to set netmask fails when the interface address is 0.0.0.0.
The kernel always keeps the netmask as 0 when the address is 0.0.0.0.
Avoid making a call to prefix length when address is 0.0.0.0

Bug: 5255172
Change-Id: Id32f7823b2230fb9ac7cd45b0df1951f11338112