audioflinger: pass return code up from startClient

Was ignoring failed start.

Bug: 65262790
Test: see bug
Change-Id: I0b1d19adfd50d2b00d86bb82f278b720fcbacdb1
diff --git a/services/oboeservice/AAudioServiceStreamMMAP.cpp b/services/oboeservice/AAudioServiceStreamMMAP.cpp
index 43595a4..47041c5 100644
--- a/services/oboeservice/AAudioServiceStreamMMAP.cpp
+++ b/services/oboeservice/AAudioServiceStreamMMAP.cpp
@@ -92,7 +92,7 @@
 
     aaudio_result_t result = AAudioServiceStreamBase::start();
     if (!mInService && result == AAUDIO_OK) {
-        startClient(mMmapClient, &mClientHandle);
+        result = startClient(mMmapClient, &mClientHandle);
     }
     return result;
 }
@@ -107,7 +107,7 @@
     aaudio_result_t result = AAudioServiceStreamBase::pause();
     // TODO put before base::pause()?
     if (!mInService) {
-        stopClient(mClientHandle);
+        (void) stopClient(mClientHandle);
     }
     return result;
 }
@@ -119,7 +119,7 @@
     aaudio_result_t result = AAudioServiceStreamBase::stop();
     // TODO put before base::stop()?
     if (!mInService) {
-        stopClient(mClientHandle);
+        (void) stopClient(mClientHandle);
     }
     return result;
 }