lightningd: free strmap of commands on shutdown.

Indirect leak of 48 byte(s) in 1 object(s) allocated from:
    #0 0x7f4c84ce4448 in malloc (/lib/x86_64-linux-gnu/libasan.so.5+0x10c448)
    #1 0x55d11b77d270 in strmap_add_ ccan/ccan/strmap/strmap.c:90
    #2 0x55d11b704603 in command_set_usage lightningd/jsonrpc.c:891
    #3 0x55d11b733cb5 in param common/param.c:295
    #4 0x55d11b6f7b37 in json_connect lightningd/connect_control.c:96
    #5 0x55d11b7042ef in setup_command_usage lightningd/jsonrpc.c:841
    #6 0x55d11b70443b in jsonrpc_command_add_perm lightningd/jsonrpc.c:863
    #7 0x55d11b704533 in jsonrpc_setup lightningd/jsonrpc.c:876
    #8 0x55d11b705695 in new_lightningd lightningd/lightningd.c:210
    #9 0x55d11b706062 in main lightningd/lightningd.c:644
    #10 0x7f4c84696b6a in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x26b6a)

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

lightningd/jsonrpc.c

@@ -876,6 +876,11 @@ static bool jsonrpc_command_add_perm(struct lightningd *ld,
 	return true;
 }
 
+static void destroy_jsonrpc(struct jsonrpc *jsonrpc)
+{
+	strmap_clear(&jsonrpc->usagemap);
+}
+
 void jsonrpc_setup(struct lightningd *ld)
 {
 	struct json_command **commands = get_cmdlist();
@@ -890,6 +895,7 @@ void jsonrpc_setup(struct lightningd *ld)
 			      commands[i]->name);
 	}
 	ld->jsonrpc->rpc_listener = NULL;
+	tal_add_destructor(ld->jsonrpc, destroy_jsonrpc);
 }
 
 bool command_usage_only(const struct command *cmd)