chore(rootfs/Dockefile): update shellcheck to v0.7.2 (#281)

See https://github.com/koalaman/shellcheck/releases/tag/v0.7.2

Author: mboersma

rootfs/Dockerfile

@@ -15,7 +15,7 @@ ENV ANSIBLE_VERSION=2.10.3 \
     PROTOBUF_VERSION=3.7.0 \
     PYJWT_VERSION=1.7.1 \
     PYWINRM_VERSION=0.4.1 \
-    SHELLCHECK_VERSION=v0.7.1 \
+    SHELLCHECK_VERSION=v0.7.2 \
     SHFMT_VERSION=3.2.2 \
     PATH=$PATH:/usr/local/go/bin:/go/bin:/usr/local/bin/docker \
     GOPATH=/go