Fix flakey test run on Cloud Functions Gen2

[psx95]

The automated tests running within CloudFunctions are flakey and often fail with the following error message -

Step #2 - "run-tests-cloudfunction": === RUN   TestBasicTrace
Step #2 - "run-tests-cloudfunction":     trace_test.go:80: Retrying GetTrace: googleapi: Error 404: Requested entity was not found., notFound
Step #2 - "run-tests-cloudfunction":     trace_test.go:80: Retrying GetTrace: googleapi: Error 404: Requested entity was not found., notFound
Step #2 - "run-tests-cloudfunction":     trace_test.go:80: Retrying GetTrace: googleapi: Error 404: Requested entity was not found., notFound
Step #2 - "run-tests-cloudfunction":     trace_test.go:80: Retrying GetTrace: googleapi: Error 404: Requested entity was not found., notFound
Step #2 - "run-tests-cloudfunction":     trace_test.go:80: Retrying GetTrace: googleapi: Error 404: Requested entity was not found., notFound
Step #2 - "run-tests-cloudfunction":     trace_test.go:80: Retrying GetTrace: googleapi: Error 404: Requested entity was not found., notFound
Step #2 - "run-tests-cloudfunction":     trace_test.go:80: Retrying GetTrace: googleapi: Error 404: Requested entity was not found., notFound
Step #2 - "run-tests-cloudfunction":     trace_test.go:80: Retrying GetTrace: googleapi: Error 404: Requested entity was not found., notFound
Step #2 - "run-tests-cloudfunction":     trace_test.go:80: Retrying GetTrace: googleapi: Error 404: Requested entity was not found., notFound
Step #2 - "run-tests-cloudfunction":     trace_test.go:80: Retrying GetTrace: googleapi: Error 404: Requested entity was not found., notFound
Step #2 - "run-tests-cloudfunction":     trace_test.go:80: Retrying GetTrace: googleapi: Error 404: Requested entity was not found., notFound
Step #2 - "run-tests-cloudfunction":     trace_test.go:85: 
Step #2 - "run-tests-cloudfunction":         	Error Trace:	trace_test.go:85
Step #2 - "run-tests-cloudfunction":         	            				trace_test.go:106
Step #2 - "run-tests-cloudfunction":         	Error:      	Received unexpected error:
Step #2 - "run-tests-cloudfunction":         	            	retryable: googleapi: Error 404: Requested entity was not found., notFound
Step #2 - "run-tests-cloudfunction":         	Test:       	TestBasicTrace
Step #2 - "run-tests-cloudfunction": --- FAIL: TestBasicTrace (14.27s)

All the other tests pass.
This issue could be transient and maybe mitigated by increasing the delay b/w the retries.