Mode change needs to handle the new send_command

We remodeled send_command to not have the "no_wait" option because it really doesn't make a lot
of sense anymore.  This slipped through the changes.

ssdrapiclient.py

@@ -34,7 +34,7 @@ def mode_handler(self, event):
         print("Change mode to {}".format(mode))
         for (slcno, slc) in self.slices.items():
             if slc['mode'].startswith('FDV'):
-                self.send_command("slice waveform_cmd {} fdv-set-mode={}".format(slcno, mode), wait=False)
+                self.send_command("slice waveform_cmd {} fdv-set-mode={}".format(slcno, mode))
 
     def send_command(self, command: str) -> Deferred:
         self.sendLine('C{}|{}'.format(self.sequence, command).encode('utf-8'))