On Windows, wait a little to see if ERROR_ACCESS_DENIED goes away.

Attempting to open a file fails with ERROR_ACCESS_DENIED if the file
is flagged for deletion but not yet actually gone (another in a long
list of reasons why Windows is broken, if you ask me).  This seems
likely to explain a lot of irreproducible failures we see in the
buildfarm.  This state generally persists for only a millisecond or so,
so just wait a bit and retry.  If it's a real permissions problem,
we'll eventually give up and report it as such.  If it's the pending
deletion case, we'll see file-not-found and report that after the
deletion completes, and the caller will treat that in an appropriate
way.

In passing, rejigger the existing retry logic for some other error
cases so that we don't uselessly wait an extra time when we're
not going to retry anymore.

Alexander Lakhin (with cosmetic tweaks by me).  Back-patch to all
supported branches, since this seems like a pretty safe change and
the problem is definitely real.

Discussion: https://postgr.es/m/16161-7a985d2f1bbe8f71@postgresql.org

src/port/open.c

@@ -111,17 +111,14 @@ pgwin32_open(const char *fileName, int fileFlags,...)
 	{
 		/*
 		 * Sharing violation or locking error can indicate antivirus, backup
-		 * or similar software that's locking the file. Try again for 30
-		 * seconds before giving up.
+		 * or similar software that's locking the file.  Wait a bit and try
+		 * again, giving up after 30 seconds.
 		 */
 		DWORD		err = GetLastError();
 
 		if (err == ERROR_SHARING_VIOLATION ||
 			err == ERROR_LOCK_VIOLATION)
 		{
-			pg_usleep(100000);
-			loops++;
-
 #ifndef FRONTEND
 			if (loops == 50)
 				ereport(LOG,
@@ -132,7 +129,27 @@ pgwin32_open(const char *fileName, int fileFlags,...)
 #endif
 
 			if (loops < 300)
+			{
+				pg_usleep(100000);
+				loops++;
+				continue;
+			}
+		}
+
+		/*
+		 * ERROR_ACCESS_DENIED can be returned if the file is deleted but not
+		 * yet gone (Windows NT status code is STATUS_DELETE_PENDING).  Wait a
+		 * bit and try again, giving up after 1 second (since this condition
+		 * should never persist very long).
+		 */
+		if (err == ERROR_ACCESS_DENIED)
+		{
+			if (loops < 10)
+			{
+				pg_usleep(100000);
+				loops++;
 				continue;
+			}
 		}
 
 		_dosmaperr(err);