[master] b12c73159 silence coverity

[Nils Goroll]

commit b12c73159f8ed75f323f988e7fae9fb05e573361
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Sun Mar 17 10:25:10 2019 +0100

    silence coverity

diff --git a/bin/varnishd/cache/cache_ban_build.c b/bin/varnishd/cache/cache_ban_build.c
index a3eae6eb2..660bdabc0 100644
--- a/bin/varnishd/cache/cache_ban_build.c
+++ b/bin/varnishd/cache/cache_ban_build.c
@@ -251,7 +251,7 @@ BAN_AddTest(struct ban_proto *bp,
 	}
 
 	op = ban_parse_oper(a2);
-	if (op < 0 ||
+	if (op < _BANS_OPER_OFF ||
 	    ((1U << BAN_OPERIDX(op)) & arg_opervalid[BAN_ARGIDX(pv->tag)]) == 0)
 		return (ban_error(bp,
 		    "expected conditional (%s) got \"%s\"",