[BUG] Unable to execute methods using cp.cache_file from saltcheck tst files

[golmaal]

Description
Any module methods using cp.cache_file are failing from tst files in saltcheck-tests.

Setup

Steps to Reproduce the behavior
Add /srv/test folder and following files in it.

find /srv/test
/srv/test
/srv/test/init.sls
/srv/test/saltcheck-tests
/srv/test/saltcheck-tests/test.tst
/srv/test/download_me.txt

cat /srv/test/init.sls
test_state:
  test.show_notification:
    - text: The test state

cat /srv/test/saltcheck-tests/test.tst
test cp.cache_file:
  module_and_function: cp.cache_file
  args:
    - salt://test/download_me.txt
    - base
  assertion: assertNotEmpty
  output_details: True

salt-call cp.cache_file salt://test/download_me.txt #WORKS
local:
    /var/cache/salt/minion/files/base/test/download_me.txt

salt-call saltcheck.run_state_tests test # DOES NOT WORK
[22:22:33.038] [ERROR   ] Unable to cache file 'salt://test/download_me.txt' from saltenv 'base'.
local:
    |_
      ----------
      test:
          ----------
          test cp.cache_file:
              ----------
              duration:
                  1.3636
              module.function [args]:
                  cp.cache_file ["salt://test/download_me.txt", "base"]
              saltcheck assertion:
                  IS NOT EMPTY False
              status:
                  Fail: value is empty
    |_
      ----------
      TEST RESULTS:
          ----------
          Execution Time:
              1.3636
          Failed:
              1
          Missing Tests:
              0
          Passed:
              0
          Skipped:
              0

Expected behavior
The execution modules should work when called by saltcheck test files as they work when called directly.

Versions Report

salt --versions-report Salt Version: Salt: 3004.1

Dependency Versions:
cffi: 1.15.0
cherrypy: unknown
dateutil: 2.6.1
docker-py: Not Installed
gitdb: Not Installed
gitpython: Not Installed
Jinja2: 2.10.1
libgit2: Not Installed
M2Crypto: 0.35.2
Mako: 1.0.6
msgpack: 1.0.3
msgpack-pure: Not Installed
mysql-python: Not Installed
pycparser: 2.14
pycrypto: Not Installed
pycryptodome: 3.12.0
pygit2: Not Installed
Python: 3.6.8 (default, Sep 10 2021, 09:13:53)
python-gnupg: 0.4.8
PyYAML: 3.12
PyZMQ: 19.0.0
smmap: Not Installed
timelib: Not Installed
Tornado: 4.5.3
ZMQ: 4.3.4

System Versions:
dist: centos 8
locale: UTF-8
machine: x86_64
release: 4.18.0-348.7.1.el8_5.x86_64
system: Linux
version: CentOS Linux 8

(Provided by running salt --versions-report. Please also mention any differences in master/minion versions.)

PASTE HERE

Additional context
Add any other context about the problem here.

[nicholasmhughes]

@wcannon @mchugh19 (or others) - can anyone speak to why saltcheck demands the local file client?

salt/salt/modules/saltcheck.py

Lines 377 to 378 in 14a932a

	# A new salt client is instantiated with the default configuration because the main module's
	# client is hardcoded to local

The test case defined in this issue works if the following line is commented:

salt/salt/modules/saltcheck.py

Line 755 in 14a932a

mlocal_opts["file_client"] = "local"

My specific use case is attempting to use file.check_managed_changes (which uses cp functionality under the hood) to see if a local file has drifted from from the source on the master during a saltcheck test.