Add createGetLinkMessage() at RtNetlinkLinkMessage

This CL adds the createGetLinkMessage() method at the
RtNetlinkLinkMessage class, that creates a link message to get the
information of a interface. The functionality is the same as
"ip link show $interface".

Bug: 364501824
Test: atest NetworkStaticLibTests

Change-Id: I87a120f488e5b6f7f24c663c68ba26835fa2157a
2 files changed