CI: Ensure EPC is always terminated in NSA-B200 pipeline

This change updates the NSA-B200 CI pipeline to guarantee that the EPC is
properly terminated regardless of pipeline success or failure. This avoids
leaving EPC processes running after failed test.

ci-scripts/xml_files/container_nsa_b200_quectel.xml

@@ -247,6 +247,7 @@
     <testCase id="060000">
       <class>UndeployCoreNetwork</class>
       <desc>Terminate EPC</desc>
+      <always_exec>true</always_exec>
       <cn_id>ltebox-nepes</cn_id>
     </testCase>