[fix][managed-ledger] fix calculation in getNumberOfEntriesInStorage

[HQebupt]

Motivation

The number of entries in storage is between markDeletePosition and lastConfirmedEntry, which the markDeletePosition is excluded, and the lastConfirmedEntry in included.
The current algorithm yields 1 more because ledger.getLastPosition().getNext() is included.

Modifications

The right way is to make the algorithm not include ledger.getLastPosition().getNext().

Verifying this change

• Make sure that the change passes the CI checks.

This change is a trivial rework / code cleanup without any test coverage.

Does this pull request potentially affect one of the following parts:

If yes was chosen, please highlight the changes

• Dependencies (does it add or upgrade a dependency): (no)
• The public API: (no)
• The schema: (no)
• The default values of configurations: (no)
• The wire protocol: (no)
• The rest endpoints: (no)
• The admin cli options: (no)
• Anything that affects deployment: (no)

Documentation

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[HQebupt]

/pulsarbot run-failure-checks

[HQebupt]

/pulsarbot run-failure-checks

[gaozhangmin]

/pulsarbot run-failure-checks

[gaozhangmin]

/pulsarbot rerun-failure-checks

[HQebupt]

/pulsarbot rerun-failure-checks

[Jason918]

Good catch.

[nicoloboschi]

The new test is failing in the release branches because, in order to pass, it needs also #14672

Caused by: java.lang.AssertionError: expected [2] but found [3]
	at org.testng.Assert.fail(Assert.java:99)
	at org.testng.Assert.failNotEquals(Assert.java:1037)
	at org.testng.Assert.assertEqualsImpl(Assert.java:140)
	at org.testng.Assert.assertEquals(Assert.java:122)
	at org.testng.Assert.assertEquals(Assert.java:907)
	at org.testng.Assert.assertEquals(Assert.java:917)
	at org.apache.bookkeeper.mledger.impl.ManagedLedgerTest.lambda$testGetNumberOfEntriesInStorage$34(ManagedLedgerTest.java:2296)
	at org.awaitility.core.AssertionCondition.lambda$new$0(AssertionCondition.java:53)
	at org.awaitility.core.ConditionAwaiter$ConditionPoller.call(ConditionAwaiter.java:222)
	at org.awaitility.core.ConditionAwaiter$ConditionPoller.call(ConditionAwaiter.java:209)
	... 4 more

I believe that we should NOT port #14672 to release branches since it's a behaviour change (even if internal). We can just modify the failing test

@HQebupt could you do it?