Wrap libpwquality PKG_CHECK_MODULES in ENABLE_SERVER test
    
    libpwquality is only needed when building a server. Don't test
    for it in a client build.
    
    https://pagure.io/freeipa/issue/6964
    https://pagure.io/freeipa/issue/5948
    https://pagure.io/freeipa/issue/2445
    https://pagure.io/freeipa/issue/298
    
    Signed-off-by: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>