Modification on SFC test Cases

Modification on SFC test Cases

- Replaced Ubuntu image with Alpine Image
- Created new variables ETH_IN, ETH_OUT, CLOUD_IMAGE_USER,
  CLOUD_IMAGE_PASS, CLOULD_IMAGE_CONSOLE specific to Cloud Image.
- Globally set suit variable for OS Prompt, user, password and console.
- During Creation of VM instance Key is ommitted as it is not required.
- Downloading VXLAN Tool is not required in this case.
- Used 512 MB and 1 CPU for Alpine Image.
- Replace curl comand with nc command.
- Replace cirros instances and create 3 instances using the opnfv image.
- Leverage SimpleHTTPServer from python to check the connection.

Change-Id: I0309c2a735664f937b41f5954ea8e6d4b44f5a71
Signed-off-by: pabitra_b <pabitra_b@hcl.com>