Error log if AZDCAP_DEBUG_LOG_LEVEL env var is not set

[eddyashton]

I believe #114 was closed prematurely. There are 2 related PRs which do not fix the underlying issue:

• Fix typo in log messages #115 fixed a typo in the error message.
• Use Cache-Control header to determine how long collateral should be cached for #122 reduced the logging severity when failing to retrieve other env vars.

However the original issue is still present - if AZDCAP_DEBUG_LOG_LEVEL is not set, the following log will be output:

Azure Quote Provider: libdcap_quoteprov.so [ERROR]: Could not retrieve environment variable for 'AZDCAP_DEBUG_LOG_LEVEL'

As far as I can tell, this comes from init_debug_log, which is reporting its errors directly with printf. I believe this error message should be dropped, to match the behaviour of dropping other similar logging messages when this env var is undefined.

[Shivr-ctrl]

Ack, Will fix it in next PR.