[SSSD] [sssd PR#1016][comment] proxy: set pwfield to x for files library

[alexey-tikhonov]

URL: https://github.com/SSSD/sssd/pull/1016
Title: #1016: proxy: set pwfield to x for files library

alexey-tikhonov commented:
"""
Code LGTM and works as expected / fixes reported issue (verified manually).

Coverity scan is clean.

But I have a question.
There are a number of other "overrides" in `confdb.c` that depend on `is_files_provider(domain)`.
Should not we apply those to proxy:files as well?

"""

See the full comment at https://github.com/SSSD/sssd/pull/1016#issuecomment-607522961