A second triggering of a prepare quorum can cause a duplicate commit message to be omitted

[Gal Rogozinski]

Since self-generated messages are only processed when gossiped back we can have a case where:

1. Prepare quorum is triggered and a commit is omitted.
2. Prepare quorum is retriggered and a duplicate commit is emitted because didSendCommitForHeightAndRound() wrongly returns false

Since network cache should mask duplicates from propagating in the network the implications are not serious. But it is unexpected behavior.

[Gal Rogozinski]

@MatheusFranco99
did you take this issue into account in MsgValidation?
I am now trying to fix this