fix(connector-fabric): mandate ssh host key verification

[petermetz]

Describe the bug

The Fabric connector does not support host key verification at the moment while connecting to a server to deploy contracts.
This is a security hole that needs to be plugged so that production deployments don't have to wonder if they are being MITM'd while deploying new contracts.

To Reproduce

Try to MITM someone who is doing a Fabric contract deployment and observe that you can do it because there was no host key verification. Oops.

Expected behavior

MITM attempt should fail as long as you do not have complete access to the target machine.

Logs/Stack traces

N/A

Screenshots

N/A

Cloud provider or hardware configuration:

Everywhere.

Operating system name, version, build:

Everywhere

Hyperledger Cactus release version or commit (git rev-parse --short HEAD):

0.4.0

Hyperledger Cactus Plugins/Connectors Used

Fabric

Additional context

https://www.ssh.com/attack/man-in-the-middle

cc: @takeutak @sfuji822 @hartm @jonathan-m-hamilton @AzaharaC @jordigiam @kikoncuo