Don't send RTT upgrade request if already RTT

If startRtt is called when the call is already an RTT call, pass down
the pipes instead of sending a new RTT request.

Bug: 80257914
Test: manual
Change-Id: I7e4f4ffea57b11156deb8765449ab2d1ca310b81
diff --git a/src/com/android/services/telephony/TelephonyConnection.java b/src/com/android/services/telephony/TelephonyConnection.java
index e80a06e..d6fb3ad 100644
--- a/src/com/android/services/telephony/TelephonyConnection.java
+++ b/src/com/android/services/telephony/TelephonyConnection.java
@@ -838,7 +838,11 @@
     public void onStartRtt(RttTextStream textStream) {
         if (isImsConnection()) {
             ImsPhoneConnection originalConnection = (ImsPhoneConnection) mOriginalConnection;
-            originalConnection.sendRttModifyRequest(textStream);
+            if (originalConnection.isRttEnabledForCall()) {
+                originalConnection.setCurrentRttTextStream(textStream);
+            } else {
+                originalConnection.sendRttModifyRequest(textStream);
+            }
         } else {
             Log.w(this, "onStartRtt - not in IMS, so RTT cannot be enabled.");
         }