More consensus fixes to ACS

[Vagabond]

This PR adds another completion check for ACS and it ensures we track we provided an input to a BBA even if that BBA was already completed.

In testing conditions it seems to resolve the intermittent consensus failure we've been tracking.

[coveralls]

Pull Request Test Coverage Report for Build 312

• 1 of 3 (33.33%) changed or added relevant lines in 1 file are covered.
• 6 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-1.3%) to 82.183%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/hbbft_acs.erl	1	3	33.33%

Files with Coverage Reduction	New Missed Lines	%
src/hbbft_acs.erl	1	86.42%
src/hbbft_cc.erl	2	65.52%
src/hbbft_bba.erl	3	83.11%

Totals
Change from base Build 309:	-1.3%
Covered Lines:	369
Relevant Lines:	449

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💛 - Coveralls

[evanmcc]

looks good

[vihu]

Looks alright 👍