s3:tldap: simplify read_ldap_more() by using asn1_peek_full_tag()

s3:tldap: simplify read_ldap_more() by using asn1_peek_full_tag()

An LDAP pdu is at least 7 bytes long, so we read at least 7 bytes,
then it's easy to use asn1_peek_full_tag() in order to find out the
whole length of the pdu on one go.

As a side effect it's now possible that wireshark can reassemble
the fragments in a socket_wrapper generated pcap file.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>