vmcheck: clean before building and adapt to new json

If the dir that was rsync'ed already contains build artifacts, we don't
want those contaminating our build process.

Closes: #336
Approved by: cgwalters

tests/vmcheck/Makefile

@@ -11,7 +11,7 @@ buildimg:
 
 build:
 	$(BUILDER_RUN) ./autogen.sh --prefix=/usr --libdir=/usr/lib64
-	$(BUILDER_RUN) make -j 4
+	$(BUILDER_RUN) sh -c 'make clean && make -j 4'
 
 install: build
 	sudo sh checkout.sh

tests/vmcheck/checkout.sh

@@ -3,7 +3,9 @@ set -euo pipefail
 
 # ugly but simple way of fetching commit we're sitting on
 commit=$(rpm-ostree status --json | \
-  python -c 'import sys, json; print json.load(sys.stdin)[0]["checksum"]')
+  python -c '
+import sys, json;
+print json.load(sys.stdin)["deployments"][0]["checksum"]')
 
 if [[ -z $commit ]] || ! ostree rev-parse $commit; then
   echo "Error while determining current commit" >&2