Recheck intensity support when restarting the driver

[mferenduros]

The check for intensity/multiecho support may fail due to a bad connection (eg. if powering or connecting a laser with urg_node already running). If the driver then resets to fix this bad connection, it should re-test for intensity/multiecho support.

[tonybaltovski]

@mferenduros am I missing something there or is the change simply in adding new variables that equal existing variables?

[mferenduros]

Hi @tonybaltovski ,

The new variables behave differently from the old ones.

publish_intensity_ will be cleared if the driver fails to initialize, whereas intensity_enabled_ reflects what was requested, and will remain true once set.

#57 describes the situation that this helps address