Howto disable LDAP PAM Auth:
/etc/nsswitch.conf
# /etc/nsswitch.conf
#
# Example configuration of GNU Name Service Switch functionality.
# If you have the `glibc-doc-reference' and `info' packages installed, try:
# `info libc "Name Service Switch"' for information about this file.
# pre_auth-client-config # passwd: compat
passwd: files
# pre_auth-client-config # group: compat
group: files
# pre_auth-client-config # shadow: compat
shadow: files
hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4
networks: files
protocols: db files
services: db files
ethers: db files
rpc: db files
# pre_auth-client-config # netgroup: nis
netgroup: nis
/etc/pam.d/common-account
account required pam_unix.so
/etc/pam.d/common-account
session required pam_unix.so
/etc/pam.d/common-auth
auth requisite pam_unix.so nullok_secure
/etc/pam.d/common-password
password requisite pam_unix.so nullok obscure md5