/pelican/monitoring directories use incorrect base path

[jhiemstrawisc]

In the upcoming 7.12 release, we created a new default directory for storing our namespace symlinks. Setting:

Cache:
  StorageLocation: /cache

Should result in the automatic generation of these directories:

/cache
  /data
  /meta
  /namespace
    /<namespace1>
    /<namespace2>
    /pelican
      /monitoring
      ...

However, the modifications to self test directory creation incorrectly used the Cache.StorageLocation as their base path, resulting in:

/cache
  /data
  /meta
  /pelican
    /monitoring
  /namespace
    /<namespace1>
    /<namespace2>

where the pelican monitoring namespace is created in the wrong spot. This prevents self test files from being read and from being cleaned up.