LogEntry: Make newFromRow work with RC object

LogEntry::newFromRow is supposed to give a RCDatabaseLogEntry
if the given row is a RC log entry. The previous code only did
this if an array was passed as the $row argument.

This adds a type cast and fixes the function so that the proper
LogEntry subclass is returned no matter what variable type is
passed to the function.

Bug: 52053
Change-Id: I6f64358837b37c54d00a7544e9e8a92c216bbe89
Merge "LogEntry: Make newFromRow work with RC object"