[CBM] IMDS not used for credentials in current 7.6.2 build

What is the problem?
We no longer check IMDS for credentials unless AWS_SDK_LOAD_SHARED_CONFIG is true.

In MB-60905 we upgraded to AWS SDK v2 but the logic was mishandled so that we disable all shared config loading unless AWS_SDK_LOAD_SHARED_CONFIG is set, rather than just the config file.