Fix field mode test case bugs

- Fix a bug where robot does not give time for /usr/local/share
  to unmount
- Fix a bug where robot assigns None to the expected value in
  Write Attribute

Resolves openbmc/openbmc-test-automation#1107

Change-Id: I28e027daf2ec598b16e3e7b40e61551d9fdae3da
Signed-off-by: Charles Paul Hofer <Charles.Hofer@ibm.com>
diff --git a/lib/rest_client.robot b/lib/rest_client.robot
index f82cc3c..8dec2d7 100644
--- a/lib/rest_client.robot
+++ b/lib/rest_client.robot
@@ -209,7 +209,7 @@
     Return From Keyword If  ${verify} == ${FALSE}
 
     ${expected_value}=  Set Variable If  '${expected_value}' == '${EMPTY}'
-    ...  ${kwargs['data']['data']}
+    ...  ${kwargs['data']['data']}  ${expected_value}
     ${value}=  Read Attribute  ${uri}  ${attr}
     Should Be Equal  ${value}  ${expected_value}