zpcictl: Use fopen() instead of open() for writes
zpcictl: Use fopen() instead of open() for writes

Be consistent with the rest of the code and use fopen() rather than
open().

Reviewed-by: Hendrik Brueckner <ea0a2d16c17dd61debc108adbc0ac849646dd099@linux.ibm.com>
Signed-off-by: Jan Höppner <96138615ab4af0813785fa10d283f3d37eca3b78@linux.ibm.com>

ibm-s390-tools/s390-tools,ibm-s390-tools/s390-tools,ibm-s390-tools/s390-tools,ibm-s390-tools/s390-tools