lmkd: add missing libcutils library to test

lmkd's test depends on the socket_local_client() function from
libcutils, but since liblog also exposes this symbol weakly, that is
the symbol that gets used instead of the intended libcutil's copy of
the symbol.

Test: build
Change-Id: I294fa157a7f50881bf6360922419976eb1ee3ac7