Clarify lockout replication issues in docs

In the "KDC replication and account lockout" section of lockout.rst,
specifically call out kprop and incremental propagation as the
mechanisms which do not replicate account lockout state, and add a
note that KDCs using LDAP may not be affected by that section's
concerns.

ticket: 7773 (new)
target_version: 1.12
tags: pullup
Portable transport enumerator
Build support for HTTPS transport
Remaining cm read/write mutator functions
Add ASN.1 codec for KKDCP's KDC-PROXY-MESSAGE
Dispatch-style protocol switching for transport
HTTPS transport (Microsoft KKDCPP implementation)
Be more exacting about the reply content-length
Remove a check on the kpasswd server's address

This test breaks when we're sending password changes over HTTP, and most
likely under NAT, too.
Track the realm name for MS-KKDCP

Always pass a realm name to set_conn_state_msg_length(), to ensure that
we include the not-actually-optional target-domain field if we're using
MS-KKDCP.