mgr/PyModule: put mgr_module_path before Py_GetPath()

mgr/PyModule: put mgr_module_path before Py_GetPath()

pip comes with _vendor/progress. so there is chance to import the vendored
version of "progress" module instead of the "progress" mgr module, and
fail to import the latter.

in this change, the order of paths are rearranged so the configured
`mgr_module_path` is put before the return value of `Py_GetPath()`.

Fixes: https://tracker.ceph.com/issues/50058
Signed-off-by: Kefu Chai <kchai@redhat.com>
(cherry picked from commit 8638f526a9d04c3dfd758073980d709165070336)

Conflicts:
	src/mgr/PyModule.cc
- nautilus has a preprocessor directive "#if PY_MAJOR_VERSION >= 3"
  which is not there in master
- since we still need to support python2, apply the same change to
  the #else branch at line 351