Fixes session id issues in adding resources

Changes include following fixes:

* Fixes HiveDriver.getSession() to get grill session from query context than thread local variable, as there are issues with thread local variable value getting changed across grill session id and hive session id.
* Fixes getSession() not to catch all exceptions and throws as GrillException.
* Fixes the first resource getting added twice because of DriverSessionStartedEvent if the first command is 'add jar'
Should be "null or empty"