[buildout] Fix develop entry in release.cfg

The path was wrong and there for the packages pulled from
the package manager rather than git.

release.cfg

@@ -6,9 +6,9 @@ eggs-directory = .buildout/eggs
 download-cache = .buildout/download-cache
 abi-tag-eggs = true
 versions = versions
-develop = beat.backend.python
-          beat.core
-          beat.cmdline
+develop = src/beat.backend.python
+          src/beat.core
+          src/beat.cmdline
           .
 
 [versions]