Fix mktemp in tesstrain_utils.sh
Fix mktemp in tesstrain_utils.sh

The commit 10f2c45c00 unified the usage of mktemp, but with a
incorrect bash syntax and unnecessary definition of LANG_CODE
and TIMESTAMP. This patch fixes the above problems.

jbarlow83/tesseract,jbarlow83/tesseract,tesseract-ocr/tesseract,jbarlow83/tesseract,tesseract-ocr/tesseract,stweil/tesseract,UB-Mannheim/tesseract,amitdo/tesseract,amitdo/tesseract,tesseract-ocr/tesseract,UB-Mannheim/tesseract,tesseract-ocr/tesseract,stweil/tesseract,stweil/tesseract,tesseract-ocr/tesseract,jbarlow83/tesseract,UB-Mannheim/tesseract,stweil/tesseract,amitdo/tesseract,stweil/tesseract,amitdo/tesseract,jbarlow83/tesseract,amitdo/tesseract,UB-Mannheim/tesseract,UB-Mannheim/tesseract