Move CredentialProviderChain instantiation during initialize

[SharpEdgeMarshall]

Closes #117

Not a ruby expert here,
Digging inside the code trying to solve #117 I saw that a new CredentialProviderChain is created for each request.
This could be "fine" if you use ENV vars or credentials file but in our case, we are using STS and this is causing a big number of request to the metadata service.

So the solution is to move the CredentialProviderChain instantiation during the initialize of the ManticoreAdapter Class

[SharpEdgeMarshall]

No feedback?

[crisidev]

We will be working on this soon. Sorry for the delay :(

Thanks a million for your contribution!

[crisidev]

This LGTM. ETA for get this fully released is beginning of next week.

[SharpEdgeMarshall]

@crisidev We are using a fork of the 6.4.1 with this PR for at least 4 months and I can confirm it works flawlessly.

[crisidev]

Ok, good to know!

We have our internal testing and release process which will help us to scope possible bugs and issues, but it is really nice to see you already have it running.

Thanks for the help! I'll keep you posted.

[salamanderrex]

LGTM. I will merge the code and release as 6.4.2.