* 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)
* Add logic for using Auth.Period when handling auth login/renew requests
* Set auth.TTL if not set in handleLoginRequest
* Always set auth.TTL = te.TTL on handleLoginRequest, check TTL and period against sys values on RenewToken
* Get sysView from le.Path, revert tests
* Add back auth.Policies
* Fix TokenStore tests, add resp warning when capping values
* Use switch for ttl/period check on RenewToken
* Move comments around
* 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
* Initial work on write concern support, set for the lifetime of the session
* Add base64 encoded value support, include docs and tests
* Handle error from json.Unmarshal, fix test and docs
* Remove writeConcern struct, move JSON unmarshal to Initialize
* Return error on empty mapping of write_concern into mgo.Safe struct
* Mention api_addr on VaultPluginTLSProvider logs, update docs
* Clarify message and mention automatic api_address detection
* Change error message to use api_addr
* Change error messages to use api_addr
