fix enforcement of tcp-clients (v1)

fix enforcement of tcp-clients (v1)

tcp-clients settings could be exceeded in some cases by
creating more and more active TCP clients that are over
the set quota limit, which in the end could lead to a
DoS attack by e.g. exhaustion of file descriptors.

If TCP client we're closing went over the quota (so it's
not attached to a quota) mark it as mortal - so that it
will be destroyed and not set up to listen for new
connections - unless it's the last client for a specific
interface.

(cherry picked from commit f97131d21b97381cef72b971b157345c1f9b4115)
(cherry picked from commit 9689ffc485df8f971f0ad81ab8ab1f5389493776)