Formally remove error from vcl_deliver VCC

Note that error wasn't actually working in vcl_deliver, and this just puts
VCC in line with the rest of Varnish. Syntax errors are better than assert
errors.

Re #1027

I'll leave it for later discussion to see if we close #1027, which is
technically a feature request now, though a request for a feature we used
to have (not sure how well it worked).

bin/varnishtest/tests/r01027.vtc

+varnishtest "Test if you can error in vcl_deliver"
+
+varnish v1 -badvcl {
+	sub vcl_deliver {
+		error 201 "ok";
+	}
+}
+

lib/libvcl/vcc_action.c

@@ -327,7 +327,7 @@ static struct action_table {
 } action_table[] = {
 	{ "error",		parse_error,
 	    VCL_MET_RECV | VCL_MET_PIPE | VCL_MET_PASS | VCL_MET_HASH |
-            VCL_MET_MISS | VCL_MET_HIT | VCL_MET_FETCH | VCL_MET_DELIVER
+            VCL_MET_MISS | VCL_MET_HIT | VCL_MET_FETCH
 	},
 
 #define VCL_RET_MAC(l, U, B)						\