If the mountpoint already exists, carry on

Signed-off-by: mulhern <[email protected]>

testlib/infra.py

@@ -605,6 +605,9 @@ def mount(self, fs_path):
         :rtype: str
         """
         mountpoint = os.path.join(self.mount_root, os.path.basename(fs_path))
-        os.mkdir(mountpoint)
+        try:
+            os.mkdir(mountpoint)
+        except FileExistsError:
+            pass
         subprocess.check_call([MOUNT, fs_path, mountpoint])
         return mountpoint