Refactor logic for obtaining host value used to submit SNI-compatible cert chain request

[atc0005]

Overview

Need to refactor the logic used to obtain the host value used in SNI-compatible cert chain request. At present, the logic is nearly 1:1 between the lscert and check_cert tool. As it happens, I just fixed a bug affecting both separately instead of fixing in one place (as ideally I would have been able to do).

I should review the code and pull out as much as possible as shared logic to dedupe future maintenance efforts.

References

• SNI-required host value not set when server value is specified as IP Address and DNS Name *is* set properly #461
• Emit host val when set & server is specified as IP #459