Remove T38 Gateway capability when detaching framehook.

SET(FAXOPT(gateway)=no) does not remove the capability when 
detaching the framehook.

small patch to fix this problem.



git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/10@338904 65c4cc65-6c06-0410-ace0-fbb531ad65f3

res/res_fax.c

@@ -2843,6 +2843,8 @@ static struct ast_frame *fax_gateway_framehook(struct ast_channel *chan, struct
 			}
 		}
 
+		details->caps &= ~AST_FAX_TECH_GATEWAY;
+
 		ao2_ref(details, -1);
 		return NULL;
 	}