Flaky test: TestCreateTraceExporter/KeepaliveParameters

[pjanotti]

@tigrannajaryan flaky test that I mentioned:

    --- FAIL: TestCreateTraceExporter/KeepaliveParameters (0.01s)
        <autogenerated>:1: 
                Error Trace:    factory_test.go:145
                Error:          Expected nil, but got: &status.statusError{Code:1, Message:"grpc: the client connection is closing", Details:[]*any.Any(nil), XXX_NoUnkeyedLiteral:struct {}{}, XXX_unrecognized:[]uint8(nil), XXX_sizecache:0}
                Test:           TestCreateTraceExporter/KeepaliveParameters

[tigrannajaryan]

Thanks.