Check board detection before erase #9
Description
Currently as per https://twitter.com/biglesp/status/1109916932105474048 and #8 the board detection routine is only triggered AFTER the erase cycle.
If the board is not recognised, it doesn't flash the board, leaving it blank after the erase.
Ideally vanguard shouldn't erase anything it knows it doesn't have a configuration to re-flash afterwards, and should fail BEFORE the erase cycle.