The libkadm5 functions hdb_open() and close around all HDB ops. This
meant the previous implementation of kadm5_lock() and unlock would
always result in a core dump. Now we hdb_open() for write in
kadm5_lock() and hdb_close() in kadm5_unlock(), with all kadm5_s_*()
functions now not opening nor closing the HDB when the server context
keep_open flag is set.
Also, there's now kadmin(8) lock and unlock commands. These are there
primarily as a way to test the kadm5_lock()/unlock() operations, but
MIT's kadmin.local also has lock/unlock commands, and these can be
useful for scripting (though they require much care).
Johan Gadsjö did a awesome analysis of the LDAP access pattens
and sent us a patch that reduced the calls the ldap server by 4
times as many. The patch was adopted and change to avoid compile
time depencies and make the determination runtime instead. Thanks!
