Python tests: Daemon ported to Windows

Instead of using os.fork (not supported on Windows),
subprocess.Popen is used and os.pipe was replaced
with Windows pipes.

To be able to identify the child process, an extra
parameter was added to daemon process '--pipe-handle'.
This parameter contains the parent Windows pipe handle
which is used by the child to notify the parent about
the startup.

The PID file is created directly on Windows, without
using a temporary file because the symbolic link does
not inherit the file lok set on the temporary file.

Signed-off-by: Paul-Daniel Boca <pboca@cloudbasesolutions.com>
Signed-off-by: Alin Balutoiu <abalutoiu@cloudbasesolutions.com>
Acked-by: Alin Gabriel Serdean <aserdean@cloudbasesolutions>
Tested-by: Alin Gabriel Serdean <aserdean@cloudbasesolutions>
Signed-off-by: Gurucharan Shetty <guru@ovn.org>

python/ovs/fatal_signal.py

@@ -59,6 +59,17 @@ def add_file_to_unlink(file):
     _files[file] = None
 
 
+def add_file_to_close_and_unlink(file, fd=None):
+    """Registers 'file' to be unlinked when the program terminates via
+    sys.exit() or a fatal signal and the 'fd' to be closed. On Windows a file
+    cannot be removed while it is open for writing."""
+    global _added_hook
+    if not _added_hook:
+        _added_hook = True
+        add_hook(_unlink_files, _cancel_files, True)
+    _files[file] = fd
+
+
 def remove_file_to_unlink(file):
     """Unregisters 'file' from being unlinked when the program terminates via
     sys.exit() or a fatal signal."""
@@ -78,6 +89,8 @@ def unlink_file_now(file):
 
 def _unlink_files():
     for file_ in _files:
+        if sys.platform == "win32" and _files[file_]:
+            _files[file_].close()
         _unlink(file_)