runtime_test.py: use track_for_cleanup for temp dir

Use track_for_cleanup for temp dir to avoid such temp
dir being not cleaned up when something goes wrong, e.g.,
building image failure.

(From OE-Core rev: 7105c9bcceda3e4defbb6aa9fb3e8fd38c1e00a2)

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oeqa/selftest/cases/runtime_test.py

@@ -153,6 +153,7 @@ class TestImage(OESelftestTestCase):
 
         # Enable package feed signing
         self.gpg_home = tempfile.mkdtemp(prefix="oeqa-feed-sign-")
+        self.track_for_cleanup(self.gpg_home)
         signing_key_dir = os.path.join(self.testlayer_path, 'files', 'signing')
         runCmd('gpg --batch --homedir %s --import %s' % (self.gpg_home, os.path.join(signing_key_dir, 'key.secret')), native_sysroot=get_bb_var("RECIPE_SYSROOT_NATIVE", "gnupg-native"))
         features += 'INHERIT += "sign_package_feed"\n'
@@ -165,9 +166,6 @@ class TestImage(OESelftestTestCase):
         bitbake('core-image-full-cmdline socat')
         bitbake('-c testimage core-image-full-cmdline')
 
-        # remove the oeqa-feed-sign temporal directory
-        shutil.rmtree(self.gpg_home, ignore_errors=True)
-
     def test_testimage_virgl_gtk(self):
         """
         Summary: Check host-assisted accelerate OpenGL functionality in qemu with gtk frontend