Only do substitutions for container path conversions with resolved paths

[AlanCoding]

SUMMARY

We have a report that, on some systems, there is a symlink /var/run -> ../run

I've added tests here that create a symlink for case-in-point like /tmp/dst -> /tmp/src

Before this change, running jobs with AWX_ISOLATION_BASE_PATH set to a symlink of this pattern would error like:

Traceback (most recent call last):
  File "/awx_devel/awx/main/tasks/jobs.py", line 469, in run
    credential.credential_type.inject_credential(credential, env, self.safe_cred_env, args, private_data_dir)
  File "/awx_devel/awx/main/models/credential/__init__.py", line 507, in inject_credential
    container_path = to_container_path(path, private_data_dir)
  File "/awx_devel/awx/main/utils/execution_environments.py", line 62, in to_container_path
    raise RuntimeError(f'Cannot convert path {path} unless it is a subdir of {private_data_dir}')
RuntimeError: Cannot convert path /tmp/foobar/awx_117_j_ds0t3g/env/tmpw093dey9 unless it is a subdir of /tmp/foobar/awx_117_j_ds0t3g

After this change, that works fine.

ISSUE TYPE

• Bugfix Pull Request

COMPONENT NAME

• API

[AlanCoding]

I'm pretty happy with this patch. It takes some thought, but this code seems clearly safer.

I moved the method to_host_path because it was only used in the tests. If our method to convert from host->container path needs updating for these reason, then it would stand to reason this method would need updating too. But we don't use it except for in the tests, so it would be pointless to do so.