Remove logging in log output function

Logging in htmlLog function prevents to use browser console as appender
for log4cplus logger since the logger goes in never end recursion in
this case.
Logging to browser console could be really useful to debug plugin.
Mem leak fix for BrowserHost::htmlLog

1. No need to use keep shared pointer to BrowserHost in AsyncLogRequest.
Weak pointer is enough in most of cases, anyway it may fail during
shutdown.
2. One more log in log output function is removed to avoid never end
recursion during shutdown in case browser console is used in log4cplus
appender as target for log messages.