Replace ntpd with chronyd in installation
Completely remove ipaserver/install/ntpinstance.py
This is no longer needed as chrony client configuration
is now handled in ipa-client-install.
Part of ipclient/install/client.py related to ntp configuration
has been refactored a bit to not lookup for srv records
and/or run chrony if not necessary.
Addresses: https://pagure.io/freeipa/issue/7024
Reviewed-By: Rob Crittenden <rcritten@redhat.com>