vmm: fix drive test error
vmm: fix drive test error

delete_dummy_path was failing because it could not find
the remove_file function. Import std::fs::self.

Signed-off-by: Andreea Florescu <f68a7d732e796861f8e79ea704b43a5ee52eddaf@amazon.com>

firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker