cronet import: set -e -x in cronet_import.sh

To better surface errors in the import script.

Test: run script
Change-Id: I833bff2aebd9a89f2cccfe3b6271db86f1bd6dab
diff --git a/Cronet/tools/import/import_cronet.sh b/Cronet/tools/import/import_cronet.sh
index 994e28a..0f04af7 100755
--- a/Cronet/tools/import/import_cronet.sh
+++ b/Cronet/tools/import/import_cronet.sh
@@ -24,6 +24,8 @@
 #   -n rev: The new revision to import.
 #   -f: Force copybara to ignore a failure to find the last imported revision.
 
+set -e -x
+
 OPTSTRING=fl:n:
 
 usage() {