CI: make docker volume always succeed in startup

Some CI users (OAI developers) expressed that the warning of the `docker
volume prune` before starting RFsim is confusing. To avoid the warning in
the HTML, force the removal; if the volume does not exist, no warning is
emitted.

To still catch possible problems, do not do this in the `terminate.xml`
so we might still see if there are other problems.

ci-scripts/xml_files/container_5g_rfsim_fdd_phytest.xml

@@ -50,7 +50,7 @@
             <class>Custom_Command</class>
             <desc>Clean-Up any residual volume</desc>
             <node>localhost</node>
-            <command>docker volume rm 5g_rfsimulator_fdd_phytest_rrc.config</command>
+            <command>docker volume rm 5g_rfsimulator_fdd_phytest_rrc.config -f</command>
         </testCase>
 
         <testCase id="000010">

ci-scripts/xml_files/container_5g_rfsim_fr2_32prb.xml

@@ -48,7 +48,7 @@
             <class>Custom_Command</class>
             <desc>Clean-Up any residual volume</desc>
             <node>localhost</node>
-            <command>docker volume rm 5g_rfsimulator_fr2_32prb_rrc.config</command>
+            <command>docker volume rm 5g_rfsimulator_fr2_32prb_rrc.config -f</command>
         </testCase>
 
         <testCase id="000000">

ci-scripts/xml_files/container_5g_rfsim_tdd_dora.xml

@@ -48,7 +48,7 @@
             <class>Custom_Command</class>
             <desc>Clean-Up any residual volume</desc>
             <node>localhost</node>
-            <command>docker volume rm 5g_rfsimulator_tdd_dora_rrc.config</command>
+            <command>docker volume rm 5g_rfsimulator_tdd_dora_rrc.config -f</command>
         </testCase>
 
         <testCase id="000000">