Add test config to libstatspull_test and libstatssocket_test

and apply mainline module test controller to it so that

the tests will only be run when statsd apex is found on device.

Bug: 154845935
Test: m mts && mts-tradefed run mts-statsd
Change-Id: I8939e68b4d4c3772e248c1960b74c0f1bd6a21a6