Even if stdlib socket is probably patched by the time StatsdClient
creates a socket, we want to import the green socket module explicitly
for better testing.
Move test_statsd.py to test_statsd_client.py so it matches the naming
convention of the rest of our test files.
Fix some patching of utils in test_statsd_client to patch
statsd_client.
Rename some vars in test_statsd_client that shadowed the statsd_client
module name.
Move some utils tests out of test_statsd_client and back into
test_utils.
Related-Change: I4b5b12a3b0288b696a39903264741bc862a94ad7
Change-Id: I3de22b7f15dd386fa9c873587782f0dfc4c42a27
b40ae84f85