doc: fslist1 "watch" option is true by default

This is not completely obvious, and one of our components even got it
wrong. But src/bridge/cockpitfslist.c implements it that way, and
several of our pages rely on it.

Also fix the default in the Python bridge.

doc/protocol.md

@@ -867,7 +867,7 @@ The following options can be specified in the "open" control message:
  * "path": The path name of the directory to watch.  This should be an
    absolute path.
  * "watch": Boolean, when true the directory will be watched and signal
-    on changes.
+    on changes. Defaults to "true"
 
 The channel will send a number of JSON messages that list the current
 content of the directory.  These messages have a "event" field with

src/cockpit/channels/filesystem.py

@@ -63,7 +63,7 @@ class FsListChannel(Channel):
 
     def do_open(self, options):
         path = options.get('path')
-        watch = options.get('watch')
+        watch = options.get('watch', True)
 
         for entry in os.scandir(path):
             self.send_entry("present", entry)