avoid a panic on failed creds polling

[jwm]

We run Vault Agent on k8s with kiam. Occasionally, the kiam-agent will be unavailable due to maintenance, which causes Agent's creds poll loop to panic.

I haven't tried running this change, but it seems pretty straightforward.

panic: interface conversion: interface {} is *errwrap.wrappedError, not string
goroutine 69 [running]:
github.com/hashicorp/vault/vendor/github.com/hashicorp/go-hclog.(*intLogger).log(0xc000701200, 0xbf48e5d44eb0be7e, 0x4a96954a2a, 0x4d2ae40, 0x4, 0x2bde115, 0x36, 0xc000c561d0, 0x2, 0x1)
	/gopath/src/github.com/hashicorp/vault/vendor/github.com/hashicorp/go-hclog/int.go:238 +0xf6f
github.com/hashicorp/vault/vendor/github.com/hashicorp/go-hclog.(*intLogger).Log(0xc000701200, 0xc000000004, 0x2bde115, 0x36, 0xc000c561d0, 0x1, 0x1)
	/gopath/src/github.com/hashicorp/vault/vendor/github.com/hashicorp/go-hclog/int.go:107 +0x1b3
github.com/hashicorp/vault/vendor/github.com/hashicorp/go-hclog.(*intLogger).Warn(0xc000701200, 0x2bde115, 0x36, 0xc000c561d0, 0x1, 0x1)
	/gopath/src/github.com/hashicorp/vault/vendor/github.com/hashicorp/go-hclog/int.go:393 +0x65
github.com/hashicorp/vault/command/agent/auth/aws.(*awsMethod).pollForCreds(0xc000702d80, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x3c)
	/gopath/src/github.com/hashicorp/vault/command/agent/auth/aws/aws.go:274 +0x202
created by github.com/hashicorp/vault/command/agent/auth/aws.NewAWSAuthMethod
	/gopath/src/github.com/hashicorp/vault/command/agent/auth/aws/aws.go:157 +0x644

[jefferai]

Superset of #7237

[jefferai]

Thanks!

[jwm]

Thanks for merging it so quickly! 🎉

[pkazi]

Hey @jwm , sorry to asking here , not a correct forum , but had no option.

As u said We run Vault Agent on k8s with kiam , I m also trying to achieve same, using aws IAM auth method for vault agent with KIAM, getting below error -

* failed to verify kiam-kiam as a valid EC2 instance in region us-east-1" backoff=1.461871503

Its coming from https://github.com/hashicorp/vault/blob/master/builtin/credential/aws/path_login.go#L1359
Can you or anyone help me how I bypass/fix this?