Remove DCHECK_NOTNULL(x) in favour of DCHECK(x != NULL)
Remove DCHECK_NOTNULL(x) in favour of DCHECK(x != NULL)

Change-Id: I5718125611291fb01f611c61184fe6c003d315ce
Reviewed-on: http://gerrit.cloudera.org:8080/664
Reviewed-by: Dan Hecht <20ebd99959f0f6e5dcb0fc319b4d8ef53a16b5fb@cloudera.com>
Tested-by: Internal Jenkins

ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC,ibmsoe/ImpalaPPC