Close peerstore and document Host Close

[aarshkshah1992]

For #1030.

[MichaelMure]

LGTM 👍

[aarshkshah1992]

ping @Stebalien

[raulk]

Is this the only correct order to call these actions? What happens if we call Close before we cancel the context?

[aarshkshah1992]

@raulk The order is NOT important. I've updated the PR.

[aarshkshah1992]

ping @Stebalien @raulk for approval.

[Stebalien]

I seem to remember that we did it this way because we don't "own" the peerstore, it may be shared. However, closing this is probably strictly better than what we currently do.

Nit: I'd use:

if pstore := h.Peerstore(); pstore != nil {
    pstore.Close()
}