Bugfix: Build docker image failed because of lacking of packages

Bugfix: Build docker image failed because of lacking of packages

JIRA: DOVETAIL-475

1. Dovetail fails to build Docker image.
Link: https://build.opnfv.org/ci/view/dovetail/job/dovetail-docker-build-push-master/162/console
   Traceback: Running setup.py install for cryptography
              c/_cffi_backend.c:15:17: fatal error: ffi.h: No such file or directory
2. Refer to https://cryptography.io/en/latest/installation/
   For Debian and Ubuntu, the following command will ensure that the required
   dependencies are installed:
   sudo apt-get install build-essential libssl-dev libffi-dev python-dev

Change-Id: Icb705823c58d8a557175d48b00745119c0a6b3b9
Signed-off-by: xudan <xudan16@huawei.com>