BUILD: Move file find_uid.c into libsss_util.so
    
    Functions from module find_uid.c were duplicated in many libraries.
    e.g. symol check_if_uid_is_active was in libsss_ad.so, libsss_ipa.so,
        libsss_krb5.so, libsss_ldap.so
    
    Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>
    Reviewed-by: Simo Sorce <simo@redhat.com>