res_rtp_asterisk: Move "Set role" warning to be debug.

In practice the set_role API callback can be invoked even
when no ICE is present on an RTP instance. This can occur
if ICE has not been enabled on it.

ASTERISK-25438 #close

Change-Id: I0e17e4316f0f0d7f095c78c3d4fd73a913b6ba69

res/res_rtp_asterisk.c

@@ -799,7 +799,7 @@ static void ast_rtp_ice_set_role(struct ast_rtp_instance *instance, enum ast_rtp
 		role == AST_RTP_ICE_ROLE_CONTROLLED ? "CONTROLLED" : "CONTROLLING", instance);
 
 	if (!rtp->ice) {
-		ast_log(LOG_WARNING, "Set role failed; no ice instance (%p)\n", instance);
+		ast_debug(3, "Set role failed; no ice instance (%p)\n", instance);
 		return;
 	}