Handle test suite teardown for VMI test suite

Changes:
    - Add directive to ignore on error during test suite exit.
      Single failure during clean up cause the whole test suite
      to failed. Suite teardown is to try clean up or restore.
      The best postitioning is at Test Teardown for a given test.

Tested:
    Run successfully test in our env
        openpower/ext_interfaces/test_vmi.robot
        openpower/ext_interfaces/test_vmicert_management.robot
        openpower/ext_interfaces/test_vmi_multiple_interfaces.robot

Change-Id: Ideb11d48862caff2aa53b49501de02d5e437ab37
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
diff --git a/openpower/ext_interfaces/test_vmicert_management.robot b/openpower/ext_interfaces/test_vmicert_management.robot
index db263b0..02b0e3a 100644
--- a/openpower/ext_interfaces/test_vmicert_management.robot
+++ b/openpower/ext_interfaces/test_vmicert_management.robot
@@ -11,7 +11,7 @@
 
 Suite Setup       Suite Setup Execution
 Test Teardown     FFDC On Test Case Fail
-Suite Teardown    Suite Teardown Execution
+Suite Teardown    Run Keyword And Ignore Error  Suite Teardown Execution
 
 Force Tags        vmi_certificate_test