Remove extbase table column cache
The extbase table column cache "extbase_typo3dbbackend_tablecolumns"
stores all DB fields of all DB tables to detect if the TCA table contains
a field named "pid".
However, if a DB table has a TCA definition but no PID, then it fails
on so many places. No need to execute a admin_get_fields call on every
method call (which caches this information - ironically - in the database).
The cache can be removed without substitution as the superfluous
check on the DB field "pid" is removed.