previous client's image is still shown on video. how to fix the bug?

[GoogleCodeExporter]

What steps will reproduce the problem?
1. one imsdroid calls one conference
2. force to stop imsdroid unconditionally without leaving the conference 
normally
3. the imsdroid joins the same conference

What is the expected output? What do you see instead?
there is still one person in the conference, which is shown on the video. But 
there are two clients image, where one image is the previous one which left 
abnormally.

What version of the product are you using? On what operating system?
doubango revision is 1157, and telepresence revision is 143. Centos 6.5 64bit 
is used.

Please provide any additional information below.
none

Original issue reported on code.google.com by andrewm...@gmail.com on 7 Nov 2014 at 10:17