Write ledger header

[eolivelli]

• write an entry to the ledger before adding it to the list of active ledgers
• this is a workaround to a possible fault case in BookKeeper when there is no entry on the Bookie and one Bookie goes down

[eolivelli]

The attached test case fails without this fix and reproduces the problems seen by @hamadodene in his test environment

[coveralls]

Pull Request Test Coverage Report for Build 690

• 24 of 33 (72.73%) changed or added relevant lines in 1 file are covered.
• 9 unchanged lines in 4 files lost coverage.
• Overall coverage increased (+0.03%) to 64.66%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
herddb-core/src/main/java/herddb/cluster/BookkeeperCommitLog.java	24	33	72.73%

Files with Coverage Reduction	New Missed Lines	%
herddb-core/src/main/java/herddb/core/TableManager.java	1	82.06%
herddb-core/src/main/java/herddb/model/Transaction.java	1	84.98%
herddb-utils/src/main/java/herddb/index/blink/BLink.java	1	71.75%
herddb-core/src/main/java/herddb/core/TableSpaceManager.java	6	79.3%

Totals
Change from base Build 683:	0.03%
Covered Lines:	16337
Relevant Lines:	25266

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💛 - Coveralls