TEST_SKEW fails if user has a .google_authenticator file

_From @ThomasHabets on October 10, 2014 8:7_

Original [issue 280](https://code.google.com/p/google-authenticator/issues/detail?id=280) created by sweharris on 2013-06-27T22:30:50.000Z:

What steps will reproduce the problem?
1. Create a ~/.google_authenticator file
2. make test

What is the expected output? What do you see instead?
Test fails in TEST_SKEW

This section in pam_google_authenticator_unittest.c
assert(pam_sm_open_session(NULL, 0, 1,
(const char *[]){ "noskewadj", 0 }) ==

does not contain the secret=/tmp/..... value from targv[0] and so if the user building the code has a defined authenticator then the test may fail.

_Copied from original issue: google/google-authenticator#279_