DP: Add a function to inherit DP options, if set
    
    Related to:
        https://fedorahosted.org/sssd/ticket/2644
    
    Adds a utility function that checks if a DP option is present in
    the subdomain_inherit list. If it is, then the option is set from source
    to destination dp_option array.
    
    Reviewed-by: Pavel Reichl <preichl@redhat.com>
    (cherry picked from commit b3d110fbc424a03674a6e50e489a7cbab9702f0b)