Modify the Pex Reactor to act as a seed node

[evan-forbes]

Blocked by

• Reactor specific peers #1728

After reactor specific peers, the pex can have its own set of peers. Every node can act as a seed node via connecting to the peer after its added, sending the entire address book, then disconnecting from the pex reactor. This essentially means that there will always be room for nodes in the network to connect to other pexes, thus acting similar to a seed node.

[evan-forbes]

there might have been some discussions elsewhere @tzdybal do you mind copy pasting those here or providing a general update on status and blockers?

[tzdybal]

I created a discussion here: #2221
It's based on my thoughts and discussion during sprint call last week.