[stable-2.9] Fix ansible-test env var mixing running commands.

(cherry picked from commit 6be4741f72)

Co-authored-by: Matt Clay <matt@mystile.com>

changelogs/fragments/ansible-test-env-alteration.yml

@@ -0,0 +1,2 @@
+bugfixes:
+    - ansible-test now properly uses a fresh copy of environment variables for each command invocation to avoid mixing vars between commands

test/lib/ansible_test/_internal/util_common.py

@@ -335,6 +335,8 @@ def intercept_command(args, cmd, target_name, env, capture=False, data=None, cwd
     """
     if not env:
         env = common_environment()
+    else:
+        env = env.copy()
 
     cmd = list(cmd)
     version = python_version or args.python_version