BUG/MINOR: tcpcheck: report correct error in tcp-check rule parser

When parsing tcp-check expect-header, a copy-paste error in the error
message causes the name of the header to be reporetd as the invalid
format string instead of its value. This is really harmless but should
be backported to all versions to help users understand the cause of the
problem when this happens. This was reported in GH issue #2586 by
@Bbulatov.

(cherry picked from commit 8a7afb6)
Signed-off-by: Amaury Denoyelle <[email protected]>

Author: wtarreau

src/tcpcheck.c

@@ -3434,7 +3434,7 @@ struct tcpcheck_rule *parse_tcpcheck_expect(char **args, int cur_arg, struct pro
 			px->conf.args.ctx = ARGC_SRV;
 			lf_expr_init(&chk->expect.hdr.value_fmt);
 			if (!parse_logformat_string(vpat, px, &chk->expect.hdr.value_fmt, 0, SMP_VAL_BE_CHK_RUL, errmsg)) {
-				memprintf(errmsg, "'%s' invalid log-format string (%s).\n", npat, *errmsg);
+				memprintf(errmsg, "'%s' invalid log-format string (%s).\n", vpat, *errmsg);
 				goto error;
 			}
 		}