Update dockerfile for core 2.67.1

[joschrew]

includes:

• update version of ocrd-core base image to latest core version
• fix work/build-dir usage and removal. Build dir in core was changed to /build/core
• remove ocrd-network logfiles, which are created through resmgr call

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 57.33%. Comparing base (d23992b) to head (5c9b5e2).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #218 +/- ## ======================================= Coverage 57.33% 57.33% ======================================= Files 12 12 Lines 1390 1390 Branches 337 337 ======================================= Hits 797 797 Misses 448 448 Partials 145 145 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.