The change of the sticky-session-force attribute requires a httpd restart.
Environment:
Apache with mod_cluster and two JBoss AS7 (standalone mode but with ha configuration).
Initial setting:

1. sticky-session=true
2. sticky-session-force=false

Example output:

27 28520f70
Switch to node c178529b
28 c178529b took 2 seconds
29 c178529b

The documentation for sticky-session-force says:

Indicates whether the httpd proxy should return an error in the event that the balancer is unable to route a request to the node to which it is stuck. This property is ignored if stickySession is false.

We change sticky-session-force to true. Now I expect an 503 error ...
But nothing happens...

5 28520f70
Switch to node c178529b
6 c178529b
7 c178529b

... after a restart of httpd and JBoss the expected error happens:

3 28520f70
Failed to open "http://ci.objectbay.com:8000/demo7/". Error code - 503.
Broken between 3 and 0 for 0 seconds.
Failed to open "http://ci.objectbay.com:8000/demo7/". Error code - 503.
Broken between 0 and 0 for 1 seconds.

It seems that the change in the settings requires a complete restart of the cluster environment.