version up: HAProxy 1.5.15

This is an important update for us because we use http-send-name-header.
A bug caused HAProxy to segfault.

component/haproxy/buildout.cfg

@@ -11,8 +11,8 @@ parts = haproxy
 
 [haproxy]
 recipe = slapos.recipe.cmmi
-url = http://www.haproxy.org/download/1.5/src/haproxy-1.5.14.tar.gz
-md5sum = ad9d7262b96ba85a0f8c6acc6cb9edde
+url = http://www.haproxy.org/download/1.5/src/haproxy-1.5.15.tar.gz
+md5sum = eeaa35744f84c92184cd735ee56dd0a3
 configure-command = true
 # If the system is running on Linux 2.6, we use "linux26" as the TARGET,
 # otherwise use "generic".