Don't dereference null pointer.

Thanks to Stéphane Castelli.
Add test for missing dst gateway too.
Check if p_routingTable is null in AsFull::~AsFull.
Avoid to dereference null pointers.
Fix test bogus-missing-gateway.
Fix another null dereference.

Also remove useless variables.
Comment unused parameter.
Add msg host on/off test
Add msg task destroy cancel test
Fix build with -Denable_jedule=ON.

Closes bug #16653.
Fix file names: they were exchanged.
Reset task before each receive.
Typos.
Split xml files to avoid memory leaks in the parser.
Remove unused variables.
Variable "duration" is never used.  Remove it.
Destroy tasks if sending has failed.
Wait for isends, and destroy comms.
Display proper execution status.
Correctly destroy tasks.