xend: Open the qemu-dm log file in append mode.

Signed-off-by: Yosuke Iwamatsu <y-iwamatsu@ab.jp.nec.com>

diff -r 926a366ca82f tools/python/xen/xend/image.py
--- a/tools/python/xen/xend/image.py	Fri Jun 20 15:21:26 2008 +0100
+++ b/tools/python/xen/xend/image.py	Wed Jun 25 16:13:55 2008 +0900
@@ -378,13 +378,9 @@ class ImageHandler:
         # keep track of pid and spawned options to kill it later
 
         self.logfile = "/var/log/xen/qemu-dm-%s.log" %  str(self.vm.info['name_label'])
-        if os.path.exists(self.logfile):
-            if os.path.exists(self.logfile + ".1"):
-                os.unlink(self.logfile + ".1")
-            os.rename(self.logfile, self.logfile + ".1")
 
         null = os.open("/dev/null", os.O_RDONLY)
-        logfd = os.open(self.logfile, os.O_WRONLY|os.O_CREAT|os.O_TRUNC|os.O_APPEND)
+        logfd = os.open(self.logfile, os.O_WRONLY|os.O_CREAT|os.O_APPEND)
         
         sys.stderr.flush()
         pid = os.fork()