Flaky or indeterministic unit test: `TestHTTPConnectWithHeaders`

[adamyeats]

--- FAIL: TestHTTPConnectWithHeaders (0.00s)
    --- FAIL: TestHTTPConnectWithHeaders/should_not_forward_http_headers (0.00s)
        driver_test.go:1248: 
            	Error Trace:	/opt/actions-runner/_work/clickhouse-datasource/clickhouse-datasource/pkg/plugin/driver_test.go:1248
            	Error:      	Not equal: 
            	            	expected: <nil>(<nil>)
            	            	actual  : status.ErrorWithSource(status.ErrorWithSource{source:"downstream", err:status.ErrorWithSource{source:"downstream", err:status.ErrorWithSource{source:"downstream", err:(*errors.errorString)(0xc000c227b0)}}})
            	Test:       	TestHTTPConnectWithHeaders/should_not_forward_http_headers
        driver_test.go:1251: 
            	Error Trace:	/opt/actions-runner/_work/clickhouse-datasource/clickhouse-datasource/pkg/plugin/driver_test.go:1251
            	Error:      	Not equal: 
            	            	expected: true
            	            	actual  : false
            	Test:       	TestHTTPConnectWithHeaders/should_not_forward_http_headers
panic: runtime error: invalid memory address or nil pointer dereference [recovered]
	panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x20 pc=0x101e11b]

Intermittent unit test failures in CI on this unit test.