qemuDomainUndefineFlags: Fix error message

https://bugzilla.redhat.com/show_bug.cgi?id=1522706

If domain is active, but the undefine API was called without the
VIR_DOMAIN_UNDEFINE_KEEP_NVRAM flag set, the following incorrect
error message is produced:

error: Requested operation is not valid: cannot delete inactive domain with nvram
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

src/qemu/qemu_driver.c

@@ -7538,7 +7538,7 @@ qemuDomainUndefineFlags(virDomainPtr dom,
             }
         } else if (!(flags & VIR_DOMAIN_UNDEFINE_KEEP_NVRAM)) {
             virReportError(VIR_ERR_OPERATION_INVALID, "%s",
-                           _("cannot delete inactive domain with nvram"));
+                           _("cannot undefine domain with nvram"));
             goto endjob;
         }
     }