BUG/MINOR: cli/mworker: can't start haproxy with 2 programs

BUG/MINOR: cli/mworker: can't start haproxy with 2 programs

When trying to start HAProxy with the master CLI and more than one
program in the configuration, it refuses to start with:

[ALERT] 013/132926 (1378) : parsing [cur--1:0] : proxy 'MASTER', another server named 'cur--1' was already defined at line 0, please use distinct names.
[ALERT] 013/132926 (1378) : Fatal errors found in configuration.

The problem is that haproxy tries to create a server for the MASTER
proxy but only the worker are supposed to be in the server list.

Fix issue #446.

Must be backported as far as 2.0.