TT#10837 Fix f508bf8: bump Dockerfile to install libfile-grep-perl into Docker container (new API test dependency)

Change-Id: If391a10613404631b88dfa91e81c4958ccea0b11

t/api-rest/Dockerfile

@@ -5,7 +5,7 @@ FROM docker.mgm.sipwise.com/sipwise-jessie: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 2017-06-30
+ENV REFRESHED_AT 2017-08-21
 
 # files that get-code generates
 COPY t/api-rest/sources.list.d/builddeps.list /etc/apt/sources.list.d/