Reset pending commands

Allow takePendingCommands to have ownership for mComamnds so commands
are reset on each call. Make reset method to be private.

Bug: 273525126
Test: manual
Change-Id: Ifecad733e5e85d475825969296ddf68081ce9e60
diff --git a/graphics/composer/aidl/vts/VtsHalGraphicsComposer3_ReadbackTest.cpp b/graphics/composer/aidl/vts/VtsHalGraphicsComposer3_ReadbackTest.cpp
index 6fa3392..b047220 100644
--- a/graphics/composer/aidl/vts/VtsHalGraphicsComposer3_ReadbackTest.cpp
+++ b/graphics/composer/aidl/vts/VtsHalGraphicsComposer3_ReadbackTest.cpp
@@ -207,9 +207,8 @@
     }
 
     void execute() {
-        const auto& commands = mWriter->getPendingCommands();
+        auto commands = mWriter->takePendingCommands();
         if (commands.empty()) {
-            mWriter->reset();
             return;
         }
 
@@ -217,7 +216,6 @@
         ASSERT_TRUE(status.isOk()) << "executeCommands failed " << status.getDescription();
 
         mReader.parse(std::move(results));
-        mWriter->reset();
     }
 
     bool getHasReadbackBuffer() {