Change chainlocks enforcing/notification flow

[UdjinM6]

Should enforce/notify when we have the block, not when we have only the header or trying to sign the tip (the later won't even work for non-masternodes).

Also, fix few related (dead)locks.

NOTE: This includes #2759 atm, will rebase after it's merged. The actual changes are in 081a40c.

[PastaPastaPasta]

081a40caeb8f2d14f8e38a3820267fd86cf3d0b2 utACK LGTM
We should probably add ChainLocks ZMQ if we haven't so far

[UdjinM6]

Rebased. Changes without whitespaces https://github.com/dashpay/dash/pull/2762/files?w=1

[PastaPastaPasta]

Not sure what the opinion is on stuff like this. Again we do it a lot in the code base, but I'm definitely not a fan

[codablock]

Hmm, this will conflict quite a bit with what I'm working on right now (what I mentioned on Slack, the rework of how EnforceBestChainLock is called to make spork12 completely obsolete)

[UdjinM6]

@codablock I don't see why/how these two would conflict cause this one just fixes it in such a way that it would actually work on all nodes and for both block->lock->notify and lock->block->notify paths but maybe you came up with a better approach which also fixes these issues while working on spork12 obsoletion, I'm fine with that, le't see :)

fyi: rebased and force-pushed to trigger Travis build, no code changes.

[UdjinM6]

closing in fav of #2765