NTP Authenticator still broken

Brief description

Issue #2731 does not seem to be fixed.

Environment

• Scapy version: 2.4.4.
• Python version: 3.8.0
• Operating System: Windows

How to reproduce

Use NTP packet capture with NTP Version 4 packets using SHA1, SHA256, SHA512 message authentication (produced by chrony or ntpd NTP server.)
Use show() command to parse packet.

Actual result

###[ UDP ]###
        sport= ntp
        dport= ntp
        len= 80
        chksum= 0xdb3b
###[ NTPHeader ]###
           leap= unknown (clock unsynchronized)
           version= 4
           mode= client
           stratum= 0
           poll= 6
           precision= 232
           delay= 0.0
           dispersion= 0.0
           ref_id= b'INIT'
           ref= 0.0
           orig= 0.0
           recv= 0.0
           sent= Tue, 02 Jun 2020 23:37:12 +0000
###[ Authenticator ]###
              padding= '\x00\x00\x00\x0c'
              key_id= 3523582088
              dgst= b4a2adc11d2dbd1420a43560bf92c6f9

Expected result

###[ UDP ]###
        sport= ntp
        dport= ntp
        len= 80
        chksum= 0xdb3b
###[ NTPHeader ]###
           leap= unknown (clock unsynchronized)
           version= 4
           mode= client
           stratum= 0
           poll= 6
           precision= 232
           delay= 0.0
           dispersion= 0.0
           ref_id= b'INIT'
           ref= 0.0
           orig= 0.0
           recv= 0.0
           sent= Tue, 02 Jun 2020 23:37:12 +0000
###[ Authenticator ]###
              padding= '\x00\x00\x00'
              key_id= 12
              dgst= d2059888b4a2adc11d2dbd1420a43560bf92c6f9

key ID was included into the padding and portion of digest was incorrectly identified as key id.

Related resources

Begin with the NTP Version 4 packet path exercised by the show() command, focusing on how the Authenticator fields are parsed for SHA1, SHA256, and SHA512 captures. Reproduce the Windows/Python 3.8 example and compare the parsed padding, key_id, and dgst with the expected output; done means the key ID is no longer taken from the digest and the authenticator fields match.