Resolve Coverity complaint
Resolve Coverity complaint

Found by a scan done on the Red Hat libvirt-cim code, but still valid
for the upstream code.

Error: SECURE_TEMP (CWE-377): [#def23]
libvirt-cim-0.6.1/src/Virt_VSMigrationService.c:504: cond_true: Condition "__retval != NULL", taking true branch
libvirt-cim-0.6.1/src/Virt_VSMigrationService.c:507: cond_false: Condition "filename == NULL", taking false branch
libvirt-cim-0.6.1/src/Virt_VSMigrationService.c:510: if_end: End of if statement
libvirt-cim-0.6.1/src/Virt_VSMigrationService.c:512: secure_temp: Calling "mkstemp(char *)" without securely setting umask first.

Resolve by adding umask code

libvirt/libvirt-cim,libvirt/libvirt-cim,libvirt/libvirt-cim