* auth/aws: Fix error with empty bound_iam_principal_arn
In cases where there doesn't need to be a bound_iam_principal_arn, i.e.,
either auth_type is ec2 or there are other bindings with the iam
auth_type, but it is specified explicitly anyway, Vault tried to parse
it to resolve to internal unique IDs. This now checks to ensure that
bound_iam_principal_arn is non-empty before attempting to resolve it.
Fixes#3837
* Fix extraneous newline
* Use version to determine plugin protocol to use
* Remove field from ServeOpts
* Fix missing assignment, handle errors
* contraint -> constraint
* Inject the version string from the vault side
* Fix the version check
* Add grpc support check to database plugins
* Default to use grpc unless missing env var or fail on contraint check
* Add GRPCSupport test
* Add greater than test case
* Add go-version dep
* Add grpc plugins
* Add grpc plugins
* Translate wrap info to/from proto
* Add nil checks
* Fix nil marshaling errors
* Provide logging through the go-plugin logger
* handle errors in the messages
* Update the TLS config so bidirectional connections work
* Add connectivity checks
* Restart plugin and add timeouts where context is not availible
* Add the response wrap data into the grpc system implementation
* Add leaseoptions to pb.Auth
* Add an error translator
* Add tests for translating the proto objects
* Fix rename of function
* Add tracing to plugins for easier debugging
* Handle plugin crashes with the go-plugin context
* Add test for grpcStorage
* Add tests for backend and system
* Bump go-plugin for GRPCBroker
* Remove RegisterLicense
* Add casing translations for new proto messages
* Use doneCtx in grpcClient
* Use doneCtx in grpcClient
* s/shutdown/shut down/
Jeff Mitchell