Add more tests since I don't get the failing Travis #166

  t/register-server-credentials.t .............. 1/?
  Failed test '302 Found'
  at t/register-server-credentials.t line 16.
         got: undef
    expected: '302'
  Looks like you failed 1 test of 9.

  ...

  Test Summary Report
  -------------------
  t/register-server-credentials.t            (Wstat: 256 Tests: 9 Failed: 1)
    Failed test:  4
    Non-zero exit status: 1
  Files=40, Tests=733, 24 wallclock secs ( 0.25 usr  0.08 sys + 19.28 cusr  1.93 csys = 21.54 CPU)
  Result: FAIL
  Failed 1/40 test programs. 1/733 subtests failed.