Code cleanup.

ExternalChangeLogTest.java:
In searchOnChangelog(), added the parameters expectedNbEntries and testName + added a loop that tries during 1s to get the expected number of entries + moved assert on nb of returned entries here + moved calls to debugAndWriteEntries() here.
Removed now unnecessary calls to Thread.sleep().
Added assertSuccessful(LDAPMessage).
Reduced scope for variables of type SearchResultDoneProtocolOp or SearchResultEntryProtocolOp + removed now useless statements making use of them.
In ECLCompatWriteReadAllOps(), removed useless calls to toLowercase().
Used Assertions.assertThat().