Try to avoid creating temp dirs in the current working directory

Try to use `mktemp -d` before falling back to calling mktemp with an
explicit template (for compat. with some BSD variants of mktemp
(see #176)).

Testing shows shows that this fixes temp dirs being created in the
current working directory on systems using a recent current GNU
coreutils mktemp variant and on systems using the mktemp variant
packaged with some macOS versions (e.g. 10.15). This may also fix the
issue on other systems as well (see
https://stackoverflow.com/a/2792789).

plumbum/machines/remote.py

@@ -325,7 +325,9 @@ def pgrep(self, pattern):
     def tempdir(self):
         """A context manager that creates a remote temporary directory, which is removed when
         the context exits"""
-        _, out, _ = self._session.run("mktemp -d tmp.XXXXXXXXXX")
+        _, out, _ = self._session.run(
+            "mktemp -d 2>/dev/null || mktemp -d tmp.XXXXXXXXXX"
+        )
         dir = self.path(out.strip())  # @ReservedAssignment
         try:
             yield dir