[cli][supervise] use last_update configuration value

pyheatpump/cli.py

@@ -157,9 +157,11 @@ def supervise(since):
 
     from .models.heatpump import Heatpump
 
-    last_update = None
-    if since:
-        last_update = int(datetime.now().strftime('%s')) - config.getint('supervisor', 'interval')
+
+    if not since:
+        last_update = 0
+    else:
+        last_update = get_last_update()
 
     h = Heatpump(mac_address, last_update)
 
@@ -204,6 +206,7 @@ def supervise(since):
     )
     if post_resp.status_code == 200:
         logger.info('POST to supervisor succeeded')
+        set_last_update(int(datetime.now().strftime('%s')))
 
     get_path = '/'.join((
         config.get('supervisor', 'get_path'),
@@ -223,5 +226,6 @@ def supervise(since):
     if h.control(control_data):
         commit()
         logger.info('GET to supervisor succeded : updated values')
+        set_last_update(int(datetime.now().strftime('%s')))
     else:
         logger.warn('Unable to set data from supervisor\n{}'.format(control_data))