Increase debounce interval to prevent double-builds.

With one of my services I'm testing with, I noticed that the service
would sometimes be restarted twice, for one file-change. Doubling the
debounce interval seems to fix the issue.

src/watch/watch.go

@@ -23,7 +23,7 @@ import (
 
 var log = logging.MustGetLogger("watch")
 
-const debounceInterval = 50 * time.Millisecond
+const debounceInterval = 100 * time.Millisecond
 
 // A CallbackFunc is supplied to Watch in order to trigger a build.
 type CallbackFunc func(*core.BuildState, []core.BuildLabel)