add libssh2

Dockerfile

@@ -60,6 +60,7 @@ RUN apt-get update && DEBIAN_FRONTEND=noninteractive apt-get install -y \
  hwloc \
  strace \
  sshpass \
+ libssh2-1-dev \
  # temporary mono dependency until .net core 2.1
  mono-runtime \
  libfsharp-core4.3-cil \