CI: RFsim tests: Wait for IP

Ensure that the UE has an IP address before continuing the test.
Otherwise, it might happen we ping before the UE is connected.

Do not do this in do-ra and phytest, as they use --noS1, which implies
statically assigned IP address, so IP address check always succeeds(!).

ci-scripts/xml_files/container_5g_e1_rfsim.xml

@@ -30,6 +30,7 @@
  000021
  000022
  000023
+ 000024
  020021
  100021
         </TestCaseRequestedList>
@@ -66,6 +67,12 @@
                 <nb_healthy>14</nb_healthy>
         </testCase>
 
+        <testCase id="000024">
+                <class>Attach_UE</class>
+                <desc>Attach OAI UE (Wait for IP)</desc>
+                <id>rfsim5g_ue rfsim5g_ue2 rfsim5g_ue3</id>
+        </testCase>
+
         <testCase id="020021">
                 <class>Ping</class>
                 <desc>Ping ext-dn from all NR-UEs</desc>