When you try to join Platform Service Controller from vSphere Web Client, the operation fails. This is known error in v6.x. To go around this error join the PSC to AD from the command line.
Open SSH session to your PSC and get into shell. Use the following command to join PSC to AD:
/opt/likewise/bin/domainjoin-cli join sefnet.local admin-user P@ssw0rd
Note that you need to replace sefnet.local with your own Active Directory name, admin-user with the user that has Domain Admin rights as well P@ssw0rd with the actual password for the admin user.