Check for VRT_fail before setting handling on return() in VCL

The compound statement doing return() in VCL may have failed for some
reason, for example running out of workspace while putting together the
reason field. The fail handling would be overwritten by the forced
handling at the end of the generated code for a return statement.

This patch adds a test for the failure condition before forcing the
handling to the result of the return statement.

lib/libvcc/vcc_action.c

@@ -366,6 +366,7 @@ vcc_act_return(struct vcc *tl, struct token *t, struct symbol *sym)
 		}
 	}
 	ERRCHK(tl);
+	Fb(tl, 1, "END_;\n");
 	if (hand == VCL_RET_FAIL)
 		Fb(tl, 1, "VRT_fail(ctx, \"Failed from VCL\");\n");
 	else