* oss/master:
Defer reader.Close that is used to determine sha256
changelog++
Avoid unseal failure if plugin backends fail to setup during postUnseal (#3686)
Add logic for using Auth.Period when handling auth login/renew requests (#3677)
plugins/database: use context with plugins that use database/sql package (#3691)
changelog++
Fix plaintext backup in transit (#3692)
Database gRPC plugins (#3666)
* Start work on context aware backends
* Start work on moving the database plugins to gRPC in order to pass context
* Add context to builtin database plugins
* use byte slice instead of string
* Context all the things
* Move proto messages to the dbplugin package
* Add a grpc mechanism for running backend plugins
* Serve the GRPC plugin
* Add backwards compatibility to the database plugins
* Remove backend plugin changes
* Remove backend plugin changes
* Cleanup the transport implementations
* If grpc connection is in an unexpected state restart the plugin
* Fix tests
* Fix tests
* Remove context from the request object, replace it with context.TODO
* Add a test to verify netRPC plugins still work
* Remove unused mapstructure call
* Code review fixes
* Code review fixes
* Code review fixes
* Return role info for each role on pathRoleList
* Change roles -> key_info, only return key_type
* Do not initialize result map in parseRole, refactor ListResponseWithInfo
* Add role list test
* encrypt/decrypt/sign/verify RSA
* update path-help and doc
* Fix the bug which was breaking convergent encryption
* support both 2048 and 4096
* update doc to contain both 2048 and 4096
* Add test for encrypt, decrypt and rotate on RSA keys
* Support exporting RSA keys
* Add sign and verify test steps
* Remove 'RSA' from PEM header
* use the default salt length
* Add 'RSA' to PEM header since openssl is expecting that
* export rsa keys as signing-key as well
* Comment the reasoning behind the PEM headers
* remove comment
* update comment
* Parameterize hashing for RSA signing and verification
* Added test steps to check hash algo choice for RSA sign/verify
* fix test by using 'prehashed'
