Upgrade psutil to 5.2.1

[fabaff]

5.2.1

Bug fixes

• [Linux] sensors_temperatures() may not show all temperatures.
• [FreeBSD] virtual_memory() may fail due to missing sysctl parameter on FreeBSD 12.
• [Linux] cpu_freq() may return an empty list.
• [Windows] Process.memory_maps() on Python 3 may raise UnicodeDecodeError.

Tested with the following configuration:

sensor:
  - platform: systemmonitor
    resources:
      - type: load_1m
      - type: 'disk_use_percent'
        arg: '/'
      - type: 'disk_use'
        arg: '/home'
      - type: 'disk_free'
        arg: '/'

[mention-bot]

@fabaff, thanks for your PR! By analyzing the history of the files in this pull request, we identified @rytilahti, @balloob and @rmkraus to be potential reviewers.