Consider using SIGINT rather than SIGTERM to stop the openconnect process from the nm-openconnect-service. OpenConnect exits immediately on SIGTERM, but does a controlled shutdown on SIGINT.

Something like the following (untested):

diff --git a/src/nm-openconnect-service.c b/src/nm-openconnect-service.c
index dc82a9f..85093b2 100644
--- a/src/nm-openconnect-service.c
+++ b/src/nm-openconnect-service.c
@@ -603,7 +603,7 @@ real_disconnect (NMVpnServicePlugin   *plugin,
        NMOpenconnectPluginPrivate *priv = NM_OPENCONNECT_PLUGIN_GET_PRIVATE (plugin);
 
        if (priv->pid) {
-               if (kill (priv->pid, SIGTERM) == 0)
+               if (kill (priv->pid, SIGINT) == 0)
                        g_timeout_add (2000, ensure_killed, GINT_TO_POINTER (priv->pid));
                else
                        kill (priv->pid, SIGKILL);
---

Forwarded from the Debian BTS: https://bugs.debian.org/820892