MINOR: cli/wait: also support an unrecoverable failure status

Since we'll support waiting for an action to succeed or permanently
fail, we need the ability to return an unrecoverable failure. Let's
add CLI_WAIT_ERR_FAIL for this. A static error message may be placed
into ctx->msg to report to the user why the failure is unrecoverable.

include/haproxy/cli-t.h

@@ -90,6 +90,7 @@ enum cli_wait_err {
 	CLI_WAIT_ERR_DONE,       // condition satisfied
 	CLI_WAIT_ERR_INTR,       // interrupted
 	CLI_WAIT_ERR_EXP,        // finished on wait expiration
+	CLI_WAIT_ERR_FAIL,       // finished early (unrecoverable)
 };
 
 enum cli_wait_cond {
@@ -100,6 +101,7 @@ struct cli_wait_ctx {
 	uint start, deadline;    // both are in ticks.
 	enum cli_wait_cond cond; // CLI_WAIT_COND_*
 	enum cli_wait_err error; // CLI_WAIT_ERR_*
+	const char *msg;         // static error message for failures if not NULL
 };
 
 struct cli_kw {

src/cli.c

@@ -2120,6 +2120,7 @@ static void cli_release_wait(struct appctx *appctx)
 	switch (ctx->error) {
 	case CLI_WAIT_ERR_EXP:      msg = "Wait delay expired.\n"; break;
 	case CLI_WAIT_ERR_INTR:     msg = "Interrupted.\n"; break;
+	case CLI_WAIT_ERR_FAIL:     msg = ctx->msg ? ctx->msg : "Failed.\n"; break;
 	default:                    msg = "Done.\n"; break;
 	}