s390x: uv-host: Fix pgm tests

We don't want to re-enter the UV call on a cc > 1 for this test.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Nico Boehr <nrb@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>