virsh: Error out if VSH_OT_STRING option has VSH_OFLAG_REQ flag

Recent commit 12bd207e fixed few
VSH_OT_STRING options that should've been VSH_OT_DATA.  That lead me to
this commit that enforces people to check that newly added options have
proper type.  Thanks to virsh erroring out with error message, this will
immediately show up in 'make check' thanks to our virsh-synopsis test.
Signed-off-by: NMartin Kletzander <mkletzan@redhat.com>

tools/virsh.c

@@ -1386,6 +1386,12 @@ vshCmddefHelp(vshControl *ctl, const char *cmdname)
                     break;
                 case VSH_OT_STRING:
                     /* OT_STRING should never be VSH_OFLAG_REQ */
+                    if (opt->flags & VSH_OFLAG_REQ) {
+                        vshError(ctl,
+                                 _("internal error: bad options in command: '%s'"),
+                                 def->name);
+                        return false;
+                    }
                     snprintf(buf, sizeof(buf), _("--%s <string>"), opt->name);
                     break;
                 case VSH_OT_DATA: