Hide Video Chat widget by default, only show when Video Chat is started.

git-svn-id: http://svn.code.sf.net/p/retroshare/code/trunk@7546 b45a01b8-16f6-495d-af2f-9b41ad6348cc
Fixed to hide the Hangup Button by default, only when call is started show

git-svn-id: http://svn.code.sf.net/p/retroshare/code/trunk@7547 b45a01b8-16f6-495d-af2f-9b41ad6348cc