Verify not yet valid certificates

- New test cases added
1. Verify_Not_Yet_Valid_Certificate_Install
2. Verify_Not_Yet_Valid_Certificate_Replace
Certificate types: CA, Client and Server

Signed-off-by: Anusha Dathatri <adathatr@in.ibm.com>
Change-Id: I4852118393331f399e646032cf34c918403f1569
diff --git a/lib/certificate_utils.robot b/lib/certificate_utils.robot
index 7a8bdcc..895ca64 100755
--- a/lib/certificate_utils.robot
+++ b/lib/certificate_utils.robot
@@ -109,7 +109,7 @@
     ...  Remove String  ${file_content}  ${private_key_content}
     ...  ELSE IF  '${cert_format}' == 'Empty Certificate Empty Privatekey'
     ...  Remove String  ${file_content}  ${cert_content}  ${private_key_content}
-    ...  ELSE IF  '${cert_format}' == 'Expired Certificate'
+    ...  ELSE IF  '${cert_format}' == 'Expired Certificate' or '${cert_format}' == 'Not Yet Valid Certificate'
     ...  OperatingSystem.Get File  ${EXECDIR}${/}${cert_dir_name}${/}cert.pem
     ...  ELSE IF  '${cert_format}' == 'Valid Certificate'
     ...  Remove String  ${file_content}  ${private_key_content}