Not Allowed Problem: Delaying Key Generation Transactions

[SurfingNerd]

currently we sometimes have a timing issue, when Node A becomes a pending validator, and immediately sends it's PART transaction.
Sometimes Node B, sees this transaction, checks if the node is allowed to do that, while not having imported the block yet, that marks Node A as pending validator.

Proposed Solution:
Instead of being that eager to send the PART transaction as fast as possible, Node A could just wait for a small delay, so Node B gets a fair chance to import the Block that marks Node A as pending validator.

This should hick up only a few unit tests that need to get adopted, and increase the timespan by a few seconds to write the contributions.
The Timing Issue in unit tests might be solvable with #2

[dforsten]

Dev Notes:

The transaction sending delay needs to be introduced at two points in the Key Generation Phase:

1. When the Key Generation Phase starts
2. When all Parts have been written

@SurfingNerd
Are the blocks at which these transitions start available through a function call in the POSDAO contracts?