Fix CodeQL note-severity alerts: confusable class and method names, and an unused verifier

[vharseko]

The last four note-severity alerts which are worth acting on: two classes named after their own supertype, two methods a capital letter apart, and a class nobody calls.

Storage implementing Storage (2 × java/class-name-matches-super-class)

org.opends.server.backends.jdbc.Storage and org.opends.server.backends.cassandra.Storage both implement org.opends.server.backends.pluggable.spi.Storage, which is why each of them has to spell the interface out in full in its own implements clause. They are renamed JDBCStorage and CASStorage, after the JEStorage and PDBStorage of the other pluggable backends. Both are constructed in exactly one place — configureStorage() of the Backend next to them — and referenced from their test cases; the configuration definitions name the Backend class, not the storage, so nothing outside the code base refers to either name.

While there, cassandra/Backend.java received the license header it was missing.

removeSubEntry next to removeSubentry (java/confusing-method-name)

SubentryManager has a private removeSubentry(Entry) which drops a subentry from both of its maps by calling a private removeSubEntry(Map, Entry) twice — the two names differ only in the case of one letter, and the call sites read as if the method called itself:

if (!removeSubEntry(dn2SubEntry, entry))
{
  removeSubEntry(dn2CollectiveSubEntry, entry);
}

The helper becomes removeSubentryFrom(Map, Entry), which says what it does and cannot be mistaken for its caller.

A hostname verifier which verifies nothing (java/unused-reference-type)

BlindHostnameVerifier is package-private, is referenced from nowhere, and its verify() returns true for every hostname. Dead code of that shape is worth removing rather than leaving around for someone to wire up: it is deleted.

Testing

• opendj-server-legacy compiles, main and test sources.
• SubentryManagerTestCase and SubentryPasswordPolicyTestCase cover the renamed helper.
• The JDBC and Cassandra backend suites drive their storage through testcontainers and skip without Docker, so the renames there are verified by the compiler and by their call sites; the classes are constructed only from Backend.configureStorage().