Zabbix

...G...... [DEV-1421] reimplemented vfs.file.md5sum in go for agent2

* commit 'b3d36a38f28e847f6174142fae40ded2ee43fc7a':
  .......... [DEV-1421] changed error message in the case of file opening failure
  ...G...... [DEV-1421] minor correction
  ...G...... [DEV-1421] add test
  ...G...... [DEV-1421] reimplemented vfs.file.md5sum in go for agent2

(cherry picked from commit 8f1435edb64cacd28b7e90c145332b1c333a4925)