If there are any errors in container setup after c.Create() in
Start(), the container will be left around, with no way to clean it up
because the handle will not be created or returned from Start.

Added a wrapper that checks for errors and performs appropriate
cleanup. Returning a cleanup function from a wrapped function instead
of just doing the cleanup before returning the error helps to ensure
that future changes that might add or change error exits can't forget
to consider a cleanup function.

Adds a check to the invalid config test case to check that a container
created with an invalid config doesn't get left behind.

Signed-off-by: Michael McCracken <mikmccra@cisco.com>

don't export an internal function, and simplify some code

Signed-off-by: Michael McCracken <mikmccra@cisco.com>

Signed-off-by: Michael McCracken <mikmccra@cisco.com>