- adapted TestUnmarshalConfig to ensure the fields are read in
- added a test to see that at least MaxOpenConns works:
- this is only exposed through (*db).Stats() in go 1.11, so this test
has a build tag
- the other two configurables can't be read back, so we've got to
trust that the mechanism works given the one instance that's tested..
Signed-off-by: Stephan Renatus <srenatus@chef.io>