[core] modify use of getrlimit() to not be fatal

modify use of getrlimit() to not be fatal if an error occurs

Some container configurations might cause getrlimit() and setrlimit() to
fail.  lighttpd will issue error trace if this occurs, but will now
proceed.

x-ref:
  "aarch64: Use architecture specific header to general syscalls"
  seccomp/libseccomp#235
  "Rasperry Docker PiHole / "Starting lighttpd" Hanging"
  pi-hole/docker-pi-hole#593
  "Pi-hole runs on podman"
  https://discourse.pi-hole.net/t/pi-hole-runs-on-podman/34719/5

src/server.c

@@ -1237,15 +1237,15 @@ static int server_main_setup (server * const srv, int argc, char **argv) {
 
 	{
 #ifdef HAVE_GETRLIMIT
-		struct rlimit rlim;
+		struct rlimit rlim = { 4096, 4096 };
 		int use_rlimit = 1;
 #ifdef HAVE_VALGRIND_VALGRIND_H
 		if (RUNNING_ON_VALGRIND) use_rlimit = 0;
 #endif
 
 		if (0 != getrlimit(RLIMIT_NOFILE, &rlim)) {
 			log_perror(srv->errh, __FILE__, __LINE__, "getrlimit()");
-			return -1;
+			use_rlimit = 0;
 		}
 
 		/**