Use a separate keyfile name for the two TLS test suites so that
they don't clash when running tests in parallel
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

The code added to validate CA certificates did not take into
account the possibility that the cacert.pem file can contain
multiple (concatenated) cert data blocks. Extend the code for
loading CA certs to use the gnutls APIs for loading cert lists.
Add test cases to check that multi-level trees of certs will
validate correctly.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

Currently a 'struct testTLSCertReq' instance is passed into
the TLS test cases. This is not flexible enough to cope with
certificate chains, where one file now corresponds to multiple
certificates. Change the test cases so that we pass in filenames
instead.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

Currently every test case in the TLS test suite generates the
certs fresh. This is a waste of time, since its parameters
don't change across test cases. Create certs once in main
method.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

The virnettlscontexttest.c tests both virNetTLSContext
and virNetTLSSession functionality. Split into two
separate tests, to make the code size more manageable
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>