Rename zuul-launcher to zuul-executor

To avoid confusion with nodepool-launcher, we've decided to rename
zuul-launcher to zuul-executor.

Change-Id: I7d03cf0f0093400f4ba2e4beb1c92694224a3e8c
Signed-off-by: Paul Belanger <pabelanger@redhat.com>
diff --git a/setup.cfg b/setup.cfg
index 972f261..86ebf65 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -25,7 +25,7 @@
     zuul-merger = zuul.cmd.merger:main
     zuul = zuul.cmd.client:main
     zuul-cloner = zuul.cmd.cloner:main
-    zuul-launcher = zuul.cmd.launcher:main
+    zuul-executor = zuul.cmd.executor:main
 
 [build_sphinx]
 source-dir = doc/source