tests: Fix Python class invocation in nvme tests

...nobody noticed this mistake, except it was deleting files in /etc/nvme

src/tests/dbus-tests/test_nvme.py

@@ -517,20 +517,20 @@ def test_hostnqn(self):
  HOSTNQN_PATH = '/etc/nvme/hostnqn'
  HOSTID_PATH = '/etc/nvme/hostid'
  FAKE_HOSTNQN = 'nqn.2014-08.org.nvmexpress:uuid:beefbeef-beef-beef-beef-beefdeadbeef'
- FAKE_HOSTID = 'beefbeef-beef-beef-beef-beefdeadbeef'
+ FAKE_HOSTID = 'beeeeeef-beef-beef-beef-beefdeadbeef'
 
  if PACKAGE_SYSCONF_DIR != '/etc':
  self.skipTest("UDisks has been configured in non-system prefix, skipping...")
 
  # save hostnqn and hostid files
  try:
- saved_hostnqn = read_file(HOSTNQN_PATH)
- self.addCleanup(write_file, HOSTNQN_PATH, saved_hostnqn)
+ saved_hostnqn = self.read_file(HOSTNQN_PATH)
+ self.addCleanup(self.write_file, HOSTNQN_PATH, saved_hostnqn)
  except:
  self.addCleanup(self.remove_file, HOSTNQN_PATH, ignore_nonexistent=True)
  try:
- saved_hostid = read_file(HOSTID_PATH)
- self.addCleanup(write_file, HOSTID_PATH, saved_hostid)
+ saved_hostid = self.read_file(HOSTID_PATH)
+ self.addCleanup(self.write_file, HOSTID_PATH, saved_hostid)
  except:
  self.addCleanup(self.remove_file, HOSTID_PATH, ignore_nonexistent=True)
  self.remove_file(HOSTNQN_PATH, ignore_nonexistent=True)