selftests: mptcp: add local variables rndh

This patch adds local variables rndh in do_transfer() functions both in
mptcp_connect.sh and simult_flows.sh, setting it with ${ns1:4}, not the
global variable rndh. The global one is hidden in the next commit.
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://lore.kernel.org/r/20240306-upstream-net-next-20240304-selftests-mptcp-shared-code-shellcheck-v2-3-bc79e6e5e6a0@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/mptcp/mptcp_connect.sh

@@ -348,6 +348,7 @@ do_transfer()
 
 	if $capture; then
 		local capuser
+		local rndh="${connector_ns:4}"
 		if [ -z $SUDO_USER ] ; then
 			capuser=""
 		else

tools/testing/selftests/net/mptcp/simult_flows.sh

@@ -139,6 +139,7 @@ do_transfer()
 
 	if $capture; then
 		local capuser
+		local rndh="${ns1:4}"
 		if [ -z $SUDO_USER ] ; then
 			capuser=""
 		else