entrypoint: default to running tests with 'ceph_preview' build tag

As this script is the heart of our ci and we generally want to test all
of go-ceph in our ci, we default to enabling ceph_preview build tag. If
we need to test only non-preview functions one can set "NO_PREVIEW" env
var to skip setting the build tag.

Signed-off-by: John Mulligan <jmulligan@redhat.com>

entrypoint.sh

@@ -123,6 +123,10 @@ if [ -n "${USE_PTRGUARD}" ]; then
     BUILD_TAGS+=",ptrguard"
 fi
 
+if [ -z "${NO_PREVIEW}" ]; then
+    BUILD_TAGS+=",ceph_preview"
+fi
+
 if [ -n "${BUILD_TAGS}" ]; then
     BUILD_TAGS="-tags ${BUILD_TAGS}"
 fi