bz 14999, log a warning and continue if files are missing from PAM

git-svn-id: svn+ssh://source-control.beyondtrust.com/sources/repo/bt-dev/trunk/Platform/src/linux@68410 9fc1c11e-11b2-4e14-94d8-6c5e05775969
bz 14997, add support for pam_sss

git-svn-id: svn+ssh://source-control.beyondtrust.com/sources/repo/bt-dev/trunk/Platform/src/linux@68411 9fc1c11e-11b2-4e14-94d8-6c5e05775969