Add configtest subcommand. skip un-ssh-able servers.

[kotakanbe]

• implementation
• test
• README

Usage: Configtest

Configtest subcommand check if vuls is able to connect via ssh to servers/containers defined in the config.toml.

$ vuls configtest --help
configtest:
        configtest
                        [-config=/path/to/config.toml]
                        [-ask-key-password]
                        [-ssh-external]
                        [-debug]

                        [SERVER]...
  -ask-key-password
        Ask ssh privatekey password before scanning
  -config string
        /path/to/toml (default "/Users/kotakanbe/go/src/github.com/future-architect/vuls/config.toml")
  -debug
        debug mode
  -ssh-external
        Use external ssh command. Default: Use the Go native implementation