[tests] fix race condition in SRP recovery reboot test

Resolve a pre-existing race condition in dind_srp_tc_11.exp:
- After the DUT reboots, the SRP server port changes.
- The test was checking 'srp client host state' immediately and
  matching 'Registered' from the pre-reboot state, before the client
  actually detected the port change and re-registered.
- Added a loop to wait for the client's registered server port to
  match the new server port before checking the host state.

Author: jwhui

tests/scripts/expect/dind_srp_tc_11.exp

@@ -357,6 +357,30 @@ sleep 5
 # Since ED_1 is already configured, it should automatically detect the new port/SN and send an update.
 send_user "Step 14: Verifying ED_1 automatically re-registers...\n"
 switch_node 4
+if {[info exists port_after]} {
+    set port_dec [expr 0x$port_after]
+    send_user "Waiting for ED_1 to update SRP server port to $port_dec...\n"
+    set port_matched false
+    for {set j 0} {$j < 20} {incr j} {
+        send "srp client server\n"
+        expect {
+            -re ".*:$port_dec" {
+                set port_matched true
+                break
+            }
+            -re "Done" {
+                # Continue
+            }
+            timeout {
+                # Continue
+            }
+        }
+        sleep 2
+    }
+    if {!$port_matched} {
+        fail "ED_1 did not update SRP server port to $port_dec"
+    }
+}
 wait_for "srp client host state" "Registered"
 expect_line "Done"