remove_tmpdir(): Support recursion / sub-directories

The existing code assumed that tmpdir only contained regular files,
not an entire hierarchy of files with sub-directories or the like.

In case sub-directories exist, the current code fails as follows:

line 176, in test_all_apps
    remove_tmpdir(tmpdir)
  File "/usr/local/lib/python3.5/dist-packages/osmopython-0.2.0-py3.5.egg/EGG-INFO/scripts/osmotestconfig.py", line 142, in remove_tmpdir
    os.unlink(os.path.join(tmpdir, f))
IsADirectoryError: [Errno 21] Is a directory: 'writtenconfig/ericsson'

Change-Id: I896b99032d94ba0cdd340a8eed7c7b625661ad69

scripts/osmotestconfig.py

@@ -15,6 +15,7 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 import os
 import os.path
+import shutil
 import time
 import sys, shutil, stat
 import tempfile
@@ -137,10 +138,7 @@ def app_exists(app_desc):
 
 
 def remove_tmpdir(tmpdir):
-    files = os.listdir(tmpdir)
-    for f in files:
-        os.unlink(os.path.join(tmpdir, f))
-    os.rmdir(tmpdir)
+    shutil.rmtree(tmpdir)
 
 
 def check_configs_tested(basedir, app_configs, ignore_configs):