In createRandomUnicastAddress, it compare the mac with the
DEFAULT_MAC_ADDRESS. However, the DEFAULT_MAC_ADDRESS is
defined as a string, so the MacAddress equals check always
return false. This patch corrects the wrong String definition
to MacAddress.
Bug: 182165856
Test: NetworkStaticLibTests
Change-Id: Ia0905bfa7a4dd723f42903f77f9d925349ce193e