Mariabackup : don't change argv[0] to "innobackupex" in innobackupex mode.

addr2line utility optionally used to output stacktrace relies relies on
correct my_progname, which is initialized from argv[0] from main function.
Thus, changing argv[0] can confuse stacktrace output.

extra/mariabackup/xtrabackup.cc

@@ -6399,8 +6399,7 @@ handle_options(int argc, char **argv, char ***argv_client, char ***argv_server)
 	for (n = 0; (*argv_client)[n]; n++) {};
  	argc_client = n;
 
-	if (strcmp(base_name(my_progname), INNOBACKUPEX_BIN_NAME) == 0 &&
-	    argc_client > 0) {
+	if (innobackupex_mode && argc_client > 0) {
 		/* emulate innobackupex script */
 		innobackupex_mode = true;
 		if (!ibx_handle_options(&argc_client, argv_client)) {
@@ -6451,7 +6450,6 @@ int main(int argc, char **argv)
 	{
 		argv++;
 		argc--;
-    argv[0] = INNOBACKUPEX_EXE;
 		innobackupex_mode = true;
 	}