end2endtest: check siks are deleted when use TempSIKs

[mariajdab]

For the anonelectionTempSIKsValidate test, at the end of the election the half of the accounts should not have a valid SIK, due they are using temporal SIK, and the other half of accounts should have it.

#1179

[coveralls]

Pull Request Test Coverage Report for Build 7034264787

• 39 of 52 (75.0%) changed or added relevant lines in 2 files are covered.
• 6 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.1%) to 61.755%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
cmd/end2endtest/helpers.go	4	8	50.0%
cmd/end2endtest/zkweighted.go	35	44	79.55%

Files with Coverage Reduction	New Missed Lines	%
vochain/state/cache.go	6	56.41%

Totals
Change from base Build 7025917591:	0.1%
Covered Lines:	14768
Relevant Lines:	23914

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💛 - Coveralls

[altergui]

i commented just minor details, really nitpicking, so LGTM