FAB-4454 Increase junit coverage for helper/Utils

. Added units tests to cover all methods
. Moved UtilsTest into the helper dir where it belongs
. Removed some assert statements in Utils.java

Change-Id: Ieab4ccd725534e64ee789c69a8ebc38b30cb3d84
Signed-off-by: Chris Murphy <chrism@fast.au.fujitsu.com>

Author: chrism28282828

src/main/java/org/hyperledger/fabric/sdk/helper/Utils.java

@@ -369,7 +369,6 @@ public static byte[] generateNonce() {
 
 
     public static String toHexString(ByteString byteString) {
-        assert (byteString != null);
         if (byteString == null) {
             return null;
         }
@@ -379,7 +378,6 @@ public static String toHexString(ByteString byteString) {
     }
 
     public static String toHexString(byte[] bytes) {
-        assert (bytes != null);
         if (bytes == null) {
             return null;
         }