CR-4097 Big code cleanup of some storage schemes.

PBKDF2PasswordStorageScheme.java, PKCS5S2PasswordStorageScheme.java:
Fixed a bug in PBKF2 + PKCS5S2 encodeOffline() methods which did not know how to deal with a byte[]. The right way was to wrap it in a ByteString like SaltedSHA1PasswordStorageScheme was already doing. BTW these encodeOffline() methods are never called from production code.
Did more code factorization.
Removed dead code in both with plainPlusSalt local variable which was not used for anything.
Fixed a few bugs in PKCS5S2 where locks where not properly taken (or carefully avoided?).
Made both PBKF2 + PKCS5S2 code look very similar now.

PBKDF2PasswordStorageSchemeTestCase.java, PKCS5S2PasswordStorageSchemeTestCase.java, PasswordStorageSchemeTestCase.java, SaltedSHA1PasswordStorageSchemeTestCase.java, SaltedSHA256PasswordStorageSchemeTestCase.java, SaltedSHA384PasswordStorageSchemeTestCase.java, SaltedSHA512PasswordStorageSchemeTestCase.java:
Removed dead code.

CryptPasswordStorageSchemeTestCase.java:
Made it reuse more code from PasswordStorageSchemeTestCase.