Avoid active connection prevent timeout of idle conns after it

Fix a logic error related to timing out of the connections
following the active one. To avoid this class of issue in
the future, create corresponding testcases, as well as some
trivial sanity testcases for both IPv4 and IPv6.

Since these tests are timing-dependent and take up time,
mark them as extended tests.

Change-Id: I2c72bad5efda7db8aa9cb05801fe47928dc47927
Signed-off-by: Andrew Yourtchenko <ayourtch@gmail.com>