MAYA-120860 Fix TestALUSDMayaPython_LayerManager random fails

[boudrey]

Disabling test_anonymousLayerSerialisation because it is randomly failing regardless of the platforms or the versions Maya/USD

[boudrey]

172/177 Test #206: TestALUSDMayaPython_LayerManager ................***Failed 7.08 sec
MAYA_DEBUG_NO_SAVE_ON_CRASH is set.
Coding Error: in _ValidateEdit at line 261 of S:/jenkins/workspace/ecg-usd-full-windows/ecg-usd-build/usd/pxr/usd/sdf/listEditor.h – Duplicate item 'anon:00000211F4A0EE40' not allowed for field 'subLayers' on </>
Warning: in _ReportErrors at line 2841 of S:\jenkins\workspace\ecg-usd-full-windows\ecg-usd-build\usd\pxr\usd\usd\stage.cpp – Could not load sublayer @anon:00000211F4A0C540@ of layer @anon:00000211F4A0F440:TestLayerManagerSerialisation-session.usda@; skipping. (instantiating stage on stage @w:/build/RelWithDebInfo/plugin/al/plugin/AL_USDMayaTestPlugin/py/testLayerManagerOutput/TestLayerManagerSerialisation.usda@ <00000211DBA0A9D0>)
File read in 0.02 seconds.
FFile read in 0.01 seconds.
.File read in 0.0082 seconds.
.File read in 0.0088 seconds.
File read in 0.012 seconds.
.
======================================================================
FAIL: test_anonymousLayerSerialisation (testLayerManager.TestLayerManagerSerialisation)
Tests multiple anonymous sublayers can be saved and restored.
----------------------------------------------------------------------
Traceback (most recent call last):
File "S:\jenkins\workspace\ecg-mayausd-branch-preflight-2022-windows\ecg-maya-usd\maya-usd\plugin\al\plugin\AL_USDMayaTestPlugin\py\testLayerManager.py", line 262, in test_anonymousLayerSerialisation
self.assertIsNotNone(sublayer02)
AssertionError: unexpectedly None

================================= Same thing on Linux 2020 =======================================

04:58:25     QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/var/tmp/runtime-administrator'
04:58:25     MAYA_DEBUG_NO_SAVE_ON_CRASH is set.
04:58:25     Coding Error: in _ValidateEdit at line 261 of /home/S/jenkins/workspace/ecg-usd-full-linux/ecg-usd-build/usd/pxr/usd/sdf/listEditor.h – Duplicate item 'anon:0x8277e70' not allowed for field 'subLayers' on </>
04:58:25     Warning: in _ReportErrors at line 2845 of /home/S/jenkins/workspace/ecg-usd-full-linux/ecg-usd-build/usd/pxr/usd/usd/stage.cpp – Could not load sublayer @anon:0x36a39a0@ of layer @anon:0x74cfe80:TestLayerManagerSerialisation-session.usda@; skipping. (instantiating stage on stage @/home/S/jenkins/workspace/ecg-mayausd-branch-preflight-2020-linux/build/RelWithDebInfo/plugin/al/plugin/AL_USDMayaTestPlugin/py/testLayerManagerOutput/TestLayerManagerSerialisation.usda@ <0x729e890>)
04:58:25     File read in  0.02 seconds.
04:58:25     FFile read in  0.017 seconds.
04:58:25     .File read in  0.013 seconds.
04:58:25     .File read in  0.014 seconds.
04:58:25     File read in  0.013 seconds.
04:58:25     .
04:58:25     ======================================================================
04:58:25     FAIL: test_anonymousLayerSerialisation (testLayerManager.TestLayerManagerSerialisation)
04:58:25     Tests multiple anonymous sublayers can be saved and restored.
04:58:25     ----------------------------------------------------------------------
04:58:25     Traceback (most recent call last):
04:58:25       File "/home/S/jenkins/workspace/ecg-mayausd-branch-preflight-2020-linux/ecg-maya-usd/maya-usd/plugin/al/plugin/AL_USDMayaTestPlugin/py/testLayerManager.py", line 263, in test_anonymousLayerSerialisation
04:58:25         self.assertIsNotNone(sublayer02)
04:58:25     AssertionError: unexpectedly None