Lemur: LDAP TLS certificate verification globally disabled enables credential interception

Lemur manages TLS certificate creation. Prior to 1.9.0, when LDAP TLS is enabled (LDAP_USE_TLS = True), Lemur's LDAP authentication module unconditionally disables TLS certificate verification at the global ldap module level. This allows a man-in-the-middle attacker positioned between Lemur and the LDAP server to intercept all authentication credentials. This vulnerability is fixed in 1.9.0.