deeplab/local_test.sh: Use 'bash' instead of 'sh' (#8534)

- Make it consistent with '/bin/bash' shebang
- Fix "Bad substitution" error in BASH_SOURCE[0]

research/deeplab/g3doc/installation.md

@@ -68,6 +68,6 @@ Quick running the whole code on the PASCAL VOC 2012 dataset:
 
 ```bash
 # From tensorflow/models/research/deeplab
-sh local_test.sh
+bash local_test.sh
 ```
 

research/deeplab/local_test.sh

@@ -19,7 +19,7 @@
 #
 # Usage:
 #   # From the tensorflow/models/research/deeplab directory.
-#   sh ./local_test.sh
+#   bash ./local_test.sh
 #
 #
 
@@ -42,7 +42,7 @@ python "${WORK_DIR}"/model_test.py
 # Go to datasets folder and download PASCAL VOC 2012 segmentation dataset.
 DATASET_DIR="datasets"
 cd "${WORK_DIR}/${DATASET_DIR}"
-sh download_and_convert_voc2012.sh
+bash download_and_convert_voc2012.sh
 
 # Go back to original directory.
 cd "${CURRENT_DIR}"