Amend python pkgs for debian-based distros

Drop python2 packages that are no longer needed. Replace other py2 pkgs
with their py3 variant.

Change-Id: Id5fc11d1ae0a7daf439c7d72f831f298f5d0ce31
diff --git a/files/debs/ldap b/files/debs/ldap
index aa3a934..54896bb 100644
--- a/files/debs/ldap
+++ b/files/debs/ldap
@@ -1,3 +1,3 @@
 ldap-utils
-python-ldap
+python3-ldap
 slapd