* Close and recreate a RemoteSigner on err
* Update changelog
* Address Anton's comments / suggestions:
- update changelog
- restart TCPVal
- shut down on `ErrUnexpectedResponse`
* re-init remote signer client with fresh connection if Ping fails
- add/update TODOs in secret connection
- rename tcp.go -> tcp_client.go, same with ipc to clarify their purpose
* account for `conn returned by waitConnection can be `nil`
- also add TODO about RemoteSigner conn field
* Tests for retrying: IPC / TCP
- shorter info log on success
- set conn and use it in tests to close conn
* Tests for retrying: IPC / TCP
- shorter info log on success
- set conn and use it in tests to close conn
- add rwmutex for conn field in IPC
* comments and doc.go
* fix ipc tests. fixes#2677
* use constants for tests
* cleanup some error statements
* fixes#2784, race in tests
* remove print statement
* minor fixes from review
* update comment on sts spec
* cosmetics
* p2p/conn: add failing tests
* p2p/conn: make SecretConnection thread safe
* changelog
* IPCVal signer refactor
- use a .reset() method
- don't use embedded RemoteSignerClient
- guard RemoteSignerClient with mutex
- drop the .conn
- expose Close() on RemoteSignerClient
* apply IPCVal refactor to TCPVal
* remove mtx from RemoteSignerClient
* consolidate IPCVal and TCPVal, fixes#3104
- done in tcp_client.go
- now called SocketVal
- takes a listener in the constructor
- make tcpListener and unixListener contain all the differences
* delete ipc files
* introduce unix and tcp dialer for RemoteSigner
* rename files
- drop tcp_ prefix
- rename priv_validator.go to file.go
* bring back listener options
* fix node
* fix priv_val_server
* fix node test
* minor cleanup and comments
