AME-5254 CR-5501 Unsynchronize thread-safe getter

git-svn-id: https://svn.forgerock.org/openam/trunk/openam@11582 0f4defcf-c51a-4c67-9f44-6fb5eba73c5d
AME-5257 CR-5499 Single SecureRandom per thread in SessionService

git-svn-id: https://svn.forgerock.org/openam/trunk/openam@11585 0f4defcf-c51a-4c67-9f44-6fb5eba73c5d