selftests: mptcp: delete uncontinuous removing ids

The removing addresses testcases can only deal with the continuous ids.
This patch added the uncontinuous removing ids support.

Signed-off-by: Geliang Tang <geliangtang@xiaomi.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>