Close all FDs in Scheduler

When scheduler calls ProxySQL_External_Scheduler::run_once() ,
after fork() we call close_all_non_term_fd() to close all file descriptors.

lib/ProxySQL_Admin.cpp

@@ -188,6 +188,24 @@ static char * load_file (const char *filename) {
 }
 */
 
+
+void close_all_non_term_fd() {
+	DIR *d;
+	struct dirent *dir;
+	d = opendir("/proc/self/fd");
+	if (d) {
+		while ((dir = readdir(d)) != NULL) {
+			if (strlen(dir->d_name) && dir->d_name[0] != '.') {
+				int fd = std::stol(std::string(dir->d_name));
+				if (fd > 2) {
+					close(fd);
+				}
+			}
+		}
+		closedir(d);
+	}
+}
+
 static int round_intv_to_time_interval(int& intv) {
 	if (intv > 300) {
 		intv = 600;
@@ -13602,6 +13620,7 @@ unsigned long long ProxySQL_External_Scheduler::run_once() {
 					exit(EXIT_FAILURE);
 				}
 				if (cpid == 0) {
+					close_all_non_term_fd();
 					char *newenviron[] = { NULL };
 					int rc;
 					rc=execve(sr->filename, newargs, newenviron);