AME-1747 / CR-2796 "Unknown error. Please contact with administrator" displayed when attempting to register user with existing username

Fixed invalid json feed. 

git-svn-id: https://svn.forgerock.org/openam/trunk/openam@7730 0f4defcf-c51a-4c67-9f44-6fb5eba73c5d
OPENAM-3416: Persistent search error during shutdown (CR-2756)

git-svn-id: https://svn.forgerock.org/openam/trunk/openam@7731 0f4defcf-c51a-4c67-9f44-6fb5eba73c5d