Fix new mount timeout log message

Problem

Currently, this log message does not contain a fixed string in MSG:

• Timeout while getting new mount (900 seconds reached). Total time trying to get new mount is 927.333838 seconds.

This makes it difficult to monitor "new mount" timeouts.

For more info check:

• https://gitlab.cern.ch/cta/operations/-/issues/1361#note_7726599

Solution

Remove any values from the string message (timeout value and max duration) and put them into a separate field.