Remove NSSConnection from the Python RPC module
    
    NSSConnection was causing a lot of trouble in the past and there is
    a lot of logic around it just to make it not fail. What's more,
    when using NSS to create an SSL connection in FIPS mode, NSS
    always requires database password which makes the `ipa` command
    totally unusable.
    
    NSSConnection is therefore replaced with Python's
    httplib.HTTPSConnection which is OpenSSL based.
    
    The HTTPSConnection is set up to handle authentication with client
    certificate for connections to Dogtag server as RA agent. It allows
    to handle client cert/private key in separate files and also
    encrypted private key files.
    
    https://fedorahosted.org/freeipa/ticket/5695
    
    Reviewed-By: Jan Cholasta <jcholast@redhat.com>