Default Vault Auth Role To Lambda Name

[abrucker235]

Changed it so that consumers could create auth roles based on lambda name and don't have to set additional variable unless they want it to be called different.

[hashicorp-cla]

All committers have signed the CLA.

[catsby]

Hey @abrucker235 - thanks for the contribution here! I admit I'm reluctant to merge this however without knowing if this is a common pattern for our users, or if it's particular to your specific usage patterns. I hope that makes sense.

[abrucker235]

@catsby this might be a pattern we use and I can see the hesitation, but its a pattern I feel helps encourage not reusing vault roles across different lambdas and practice least access. Technically this doesn't turn off the original capability.