BUG/MINOR: applet: make the call_rate only count the no-progress calls

BUG/MINOR: applet: make the call_rate only count the no-progress calls

This is very similar to what we did in commit 6c539c4b8 ("BUG/MINOR:
stream: make the call_rate only count the no-progress calls"), it's
better to only count the call rate with no progress than to count all
calls and try to figure if there's no progress, because a fast running
applet might once satisfy the whole condition and trigger the bug. This
typically happens when artificially limiting the number of messages sent
at once by an applet, but could happen with plenty of highly interactive
applets.

This patch could be backported to stable versions if there are any
indications that it might be useful there.