Prior to this commit, if a created but exited container bound a port,
and a new container grabed that same port (say for an ssh port forward),
when the initial container came back up it would fail because the port
also got bound to the second container. This commit fixes that behavior
by first looking at what containers are already bound prior to creating
a container.
When using pty=true, removing files using sudo may request confirmation,
which will hang the connection.
Similarly, sometimes assumptions about file existence may be wrong and
in those cases it seems better to continue on as long as the file does
not exist, so -f makes sense there, too.
