TT#42565 Fix 2930237: bump Dockerfile version to trigger docker rebuild

We have added new dependency in commit 2930237, but we also need to bump
Dockerfile version so Jenkins will rebuild docker container.

Change-Id: I1655af44d9e71c49473596a25e1cc9dbe617dbfa

t/api-rest/Dockerfile

@@ -5,7 +5,7 @@ FROM docker.mgm.sipwise.com/sipwise-stretch:latest
 # is updated with the current date. It will force refresh of all
 # of the base images and things like `apt-get update` won't be using
 # old cached versions when the Dockerfile is built.
-ENV REFRESHED_AT 2017-11-22
+ENV REFRESHED_AT 2018-08-10
 
 # files that get-code generates
 COPY t/api-rest/sources.list.d/builddeps.list /etc/apt/sources.list.d/