Don't install sudo on labs.  We use sudo-ldap instead.

This is a modification of Change-Id: If3233ed70b4b4b232685f4db932e548ad1c48f56

sudo-ldap and sudo are either/or.  The above change installed sudo on labs
instances, removing sudo-ldap, and breaking some things.

Change-Id: If45629be89cf57ab77d7d29dd8047fbc3b897866
Merge "Don't install sudo on labs.  We use sudo-ldap instead." into production