Client install checks for nss_ldap
    
    In order to check presence of nss_ldap or nss-pam-ldapd when installing
    client with '--no-sssd' option there was added code into ipa-client-install.
    Checking is based on existence of one of nss_ldap configuration files.
    This configuration could be in 'etc/ldap.conf', '/etc/nss_ldap.conf' or
    '/etc/libnss_ldap.conf'. Optionaly the nss_ldap could cooperate with
    pam_ldap module and hence the presence of it is checked by looking for
    'pam_ldap.conf' file. Existence of nss-pam-ldapd is checked against
    existence of 'nslcd.conf' file. All this checking is done by function
    nssldap_exists(). Because both modules are maintained by two different
    functions, the function returns tuple containing return code and dictionary
    structure - its key is name of target function and value is list of existing
    configuration files. Files to check are specified inside the
    nssldap_exists() function. nssldap_exists() also returns True if any of
    the mandatory files was found, otherwise returns False.
    
    In order to fit the returned values, the functions
    configure_{ldap|nslcd}_conf() were slightly modified. They accept one more
    parameter which is list of existing files.  They are not checking existence
    of above mentioned files anymore.
    
    https://fedorahosted.org/freeipa/ticket/2063