Apparmor on Ubuntu prevents slapd from using the Unix domain socket we
want it to. The fix is to copy the slapd executable into the objdir,
which disables the apparmor profile for slapd.
Also, make sure the ldapi: URI has the right path for the socket in
krb5.conf.
This fixes the following problems from #210:
- hdb_ldap doesn't load even when installed correctly
- loadable hdb backends not listed by kdc --builtin-hdb
Not fixed:
- hdb_ldap.so not installed in plugin dir
