Workaround for IMPALA-2062
Workaround for IMPALA-2062

Impala redefines DCHECK_NOTNULL in a way that changes the originally
intended semantics. If common/logging.h ends up being included and
the returned value of DCHECK_NOTNULL is used that statement won't
compile in release mode. KuduScanNode was committed using this macro
as originally intended, meaning that it wouldn't compile in release mode.

This macro pulls the DCHECK_NOTNULL into a regular DCHECK statement.

Change-Id: I6375666b7d6e33fa754c01bc2b37c3bbaff4e6a9
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/6897
Tested-by: jenkins
Reviewed-by: Martin Grund <2546548d516fa64c411fde8242af35f3f80ad31f@cloudera.com>

kapilrastogi/Impala,kapilrastogi/Impala,kapilrastogi/Impala,kapilrastogi/Impala,kapilrastogi/Impala,kapilrastogi/Impala,kapilrastogi/Impala