tests: Wait explicitly for the guest vm to boot

Instead of blindly waiting for 20-40s for the guest VM to boot, this
patch waits the notification from the guest VM explicitly by using a
simple TcpListener on the host and a custom systemd service in the
guest.

This patch also ported few tests to use this new machanism, while more
tests are to be ported.

Signed-off-by: Bo Chen <chen.bo@intel.com>

Cargo.toml

@@ -16,6 +16,7 @@ lto = true
 anyhow = "1.0"
 api_client = { path = "api_client" }
 clap = { version = "2.33.3", features = ["wrap_help"] }
+epoll = ">=4.0.1"
 hypervisor = { path = "hypervisor" }
 libc = "0.2.80"
 log = { version = "0.4.11", features = ["std"] }