fastbootd: Fix transport ownership.

This change moves Transport ownership back out of FastBootDriver.
Callers of set_transport must ensure that the previous transport is
destroyed. In addition, deleting a transport now ensures that it is
closed.

Bug: 78793464
Test: fastboot, fuzzy_fastboot works
Change-Id: I8f9ed2f7d5b09fd0820b2677d087a027378f26db
diff --git a/fastboot/usb_windows.cpp b/fastboot/usb_windows.cpp
index 8c60a71..b00edb3 100644
--- a/fastboot/usb_windows.cpp
+++ b/fastboot/usb_windows.cpp
@@ -69,7 +69,7 @@
 class WindowsUsbTransport : public UsbTransport {
   public:
     WindowsUsbTransport(std::unique_ptr<usb_handle> handle) : handle_(std::move(handle)) {}
-    ~WindowsUsbTransport() override = default;
+    ~WindowsUsbTransport() override;
 
     ssize_t Read(void* data, size_t len) override;
     ssize_t Write(const void* data, size_t len) override;
@@ -250,6 +250,10 @@
     }
 }
 
+WindowsUsbTransport::~WindowsUsbTransport() {
+    Close();
+}
+
 int WindowsUsbTransport::Close() {
     DBG("usb_close\n");