Remove legacy debian.log file

With aosp/3531212, debian.log becomes dir instead of file, so remove the
file before creating dir.

Bug: n/a
Test: run terminal in the old version, and then upgrade
Change-Id: I8a949d2108927ba4b17074295861d3b8e784cdcc
diff --git a/android/TerminalApp/java/com/android/virtualization/terminal/Logger.kt b/android/TerminalApp/java/com/android/virtualization/terminal/Logger.kt
index 4162247..ba03716 100644
--- a/android/TerminalApp/java/com/android/virtualization/terminal/Logger.kt
+++ b/android/TerminalApp/java/com/android/virtualization/terminal/Logger.kt
@@ -47,6 +47,10 @@
         }
 
         try {
+            if (Files.isRegularFile(dir)) {
+                Log.i(tag, "Removed legacy log file: $dir")
+                Files.delete(dir)
+            }
             Files.createDirectories(dir)
             deleteOldLogs(dir, 10)
             val logPath = dir.resolve(LocalDateTime.now().toString() + ".txt")