Fix getting flavor ID when using python-openstackclient==7.0.0

Change-Id: Ib3e8af1a6a6d86e489b7734a8a9bf5597fa8326c
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>

robot-systest/lib/openstack_lib.resource

@@ -31,7 +31,7 @@ Get Server Flavor ID
     [Documentation]   Get from Openstack the flavor id of a server/VM passed as argument.
     [Arguments]   ${server_id}
     Should Not Be Empty   ${server_id}
-    ${rc}   ${stdout}=   Run And Return Rc And Output   openstack server show ${server_id} | grep flavor | awk 'NR>1{print $1}' RS='(' FS=')'
+    ${rc}   ${stdout}=   Run And Return Rc And Output   openstack server show ${server_id} -c flavor -f value |yq -r '.id'
     Log   ${stdout}
     Should Be Equal As Integers   ${rc}   ${SUCCESS_RETURN_CODE}
     RETURN   ${stdout}