SW-61. Make openTunLinux handling of v6ToInternet event like Windows impl.

openTunLinux.py -- Add try/except handler, and throw ValueError.
openLbr.py ------- Use dispatch() rather than _dispatchProtocol() for
v6ToInternet signal since function call does not use return value.
Merge pull request #28 from kb2ma/develop_SW-61

SW-61. Make openTunLinux handling of v6ToInternet event like Windows imp...