cast to varchar in mssql query (system tests)

Author: mykola-elastic

packages/sql_input/_dev/test/system/test-mssql-config.yml

@@ -3,4 +3,4 @@ vars:
   hosts:
     - sqlserver://SA:1234_asdf@{{Hostname}}
   driver: "mssql"
-  sql_queries: "- query: SELECT counter_name, instance_name, cntr_value FROM sys.dm_os_performance_counters\n  response_format: table\n- query: go\n  response_format: table"
+  sql_queries: "- query: SELECT counter_name, instance_name, CAST(cntr_value AS VARCHAR(20)) AS cntr_value FROM sys.dm_os_performance_counters\n  response_format: table\n- query: go\n  response_format: table"