[Fix-bug] Here is a TypeError when running FUNCovsdbtest.

2018-03-19 10:45:22,665 - FUNCovsdbtest - ERROR - ONOSbench1: Uncaught exception!
Traceback (most recent call last):
  File "/home/sdn/Workspace/OnosSystemTest/TestON/drivers/common/cli/onosdriver.py", line 798, in createCellFile
    cellFile.write( mnString + "\"" + mnIpAddrs + "\"\n" )
TypeError: cannot concatenate 'str' and 'OvsdbDriver' objects

Change-Id: Id6cba6abd8fb042871c0636da5ef5f7a67809823
diff --git a/TestON/drivers/common/cli/onosdriver.py b/TestON/drivers/common/cli/onosdriver.py
index 6058cbd..8324677 100755
--- a/TestON/drivers/common/cli/onosdriver.py
+++ b/TestON/drivers/common/cli/onosdriver.py
@@ -795,7 +795,7 @@
                 tempCount = tempCount + 1
 
             cellFile.write( "export OCI=$OC1\n" )
-            cellFile.write( mnString + "\"" + mnIpAddrs + "\"\n" )
+            cellFile.write( mnString + "\"" + str(mnIpAddrs) + "\"\n" )
             cellFile.write( appString + "\n" )
             cellFile.write( onosGroup + "\n" )
             cellFile.write( onosUser + "\n" )