config: Use talloc_free() to free "route" strings

Adding redundant routes triggers a glibc assertion on startup.  The offending
config file contained:

    route = 192.168.1.0/255.255.255.0
    route = default

The assertion:

    # ./src/ocserv -c ocserv.conf -f
    *** Error in `./src/ocserv': munmap_chunk(): invalid pointer: 0x0000000001703470 ***
    Aborted (core dumped)

Fix this by calling the correct free() function.

src/config.c

@@ -718,7 +718,7 @@ unsigned force_cert_auth;
 		    strcmp(config->network.routes[j], "default") == 0) {
 		    	/* set default route */
 			for (i=0;i<j;i++)
-				free(config->network.routes[i]);
+				talloc_free(config->network.routes[i]);
 			config->network.routes_size = 0;
 			break;
 		}