nbd-server: drop the double-fork

... as this breaks as systemd service: This is of type 'forking', so the
(first) fork becomes the main and controlling process. The second fork
makes the main process exit, and the service is stopped.

Calling setsid() should be sufficient to detatch from terminal.

Closes: #182

Author: eworm-de

nbd-server.c

@@ -3816,12 +3816,6 @@ void daemonize() {
         if(dup2(2, newfd) < 0) {
                 err("dup2 stderr");
         }
-        child=fork();
-        if(child < 0) {
-                err("fork");
-        } else if(child > 0) {
-                exit(EXIT_SUCCESS);
-        }
 	FILE*pidf=fopen(pidfname, "w");
 	if(pidf) {
 		fprintf(pidf,"%d\n", (int)getpid());