ldb: Do not build libldb-cmdline when using system ldb.

ldb: Do not build libldb-cmdline when using system ldb.

Cleanup leftover include and linking of libldb-cmdline in
oLschema2ldif. Do not build libldb-cmdline anymore when using the
system ldb, oLschema2ldif was the only reason for building
libldb-cmdline.

Signed-off-by: Jeroen Dekkers <jeroen@dekkers.ch>
Reviewed-by: Andreas Schneider <asn@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Tue Sep 10 12:52:26 CEST 2013 on sn-devel-104