Do not log error when removing a non-existing file

When the uninstaller tries to remove /etc/systemd/system/httpd.d/ipa.conf and
the file does not exist, only log to debug instead of error.

https://fedorahosted.org/freeipa/ticket/6012

Reviewed-By: Martin Basti <mbasti@redhat.com>

ipaplatform/redhat/tasks.py

@@ -29,6 +29,7 @@ import os
 import socket
 import base64
 import traceback
+import errno
 
 from cffi import FFI
 from ctypes.util import find_library
@@ -466,6 +467,12 @@ class RedHatTaskNamespace(BaseTaskNamespace):
         try:
             os.unlink(paths.SYSTEMD_SYSTEM_HTTPD_IPA_CONF)
         except OSError as e:
+            if e.errno == errno.ENOENT:
+                root_logger.debug(
+                    'Trying to remove %s but file does not exist',
+                    paths.SYSTEMD_SYSTEM_HTTPD_IPA_CONF
+                )
+            else:
                 root_logger.error(
                     'Error removing %s: %s',
                     paths.SYSTEMD_SYSTEM_HTTPD_IPA_CONF, e