Fix command test wrt gnutls initialize & fix debugging

Fix command test wrt gnutls initialize & fix debugging

The VIR_TEST_DEBUG and VIR_TEST_VERBOSE env vars did not work
because we replaced 'environ' with 'newenv'. Simply calling
virTestGetDebug/Verbose() before replacing the 'environ' ensures
we have processed the env variables.

The gnutls initialization code opens /dev/urandom and keeps that
FD around for later use. We have code which kills off FDs 3-5
to avoid interfereing with our test case. Move the virInitialize
call before this point, so it kills off the gnutls /dev/urandom
FD which is irrelevant for testing purposes

* tests/commandtest.c: Fix test debugging & make it robust against
  opened FDs