Long waiting and high processor use during connecting/bootstrap

[loziniak]

Hello.

I've successfully connected to current testnet. The experience is good, although there are two problems:

1. Connection process hangs for a long time (about 1-2 minutes), because of a bootstrap server not responding.
2. After the process finishes, the bootstrap takes lots of resources in the background.

I made a screenshot:

Hanging connection is marked with green color, and processor use spikes during bootstrap with red.

Perhaps each bootstrap server could be queried in separate thread, to allow the process succeed quickly even with some servers down? And maybe it's not necessary to try all nodes everytime the background scan fires, unless there is not enough nodes for a client?