The getaddr msg is usually replied to with an addr msg, but if
the other peer does not have any addresses to share it will not
reply at all (instead of replying with an addr msg with 0 addresses).
Therefore, the getaddr msg is not guaranteed a reply, so this commit
removes it from stall detection to avoid incorrectly kicking
such peers.

When a persistent peer is disconnected (for example due to a
network timeout), a connection retry is issued. The logic for
doing so failed to remove the peer from the peerState, causing
dead peer connections to fill the peerState. Since connections
in the peerState are counted towards the maxPeers limit, this
would cause btcd to eventually stop retrying connection.

This commit fixes the issue by properly removing the peer from
the peerState.

Reviewed changelog and fixed 2 tiny typos.

 guidelinestherin ---> guidelines therein.

Changed the order of return values described in the docs to be
consistent with the function’s actual return value signature.

Found via github.com/mvdan/interfacer.

Also disconnect the failed peer to allow the peerDoneHandler goroutine
to exit, instead of hanging around. Fixes btcsuite#583.

Contains the following upstream commits:
- 87182a2
  - This commit does not apply to Decred so it has been reverted
- 89af747
  - This commit has already been cherry picked and is a NOOP
- d0cdd53
  - This commit has already been cherry picked and is a NOOP
- df20c10
- ff0c787
- 6e133b5
- 34a94b7
- 14ccab8

Contains the following upstream commits:
- 829e87a
  - This commit does not apply to Decred so it has been reverted
- d0cdd53
  - This commit does not apply to Decred so it has been reverted
- 7996eb1
  - This commit has already been cherry picked and is a NOOP
- 1944637
- f5ded65
- 407fcc2