tail: fix the checks if the file was rotated

The freopen(3) was replaced with fileargs_open(3) and fclose(3).
In the following function, we skip if the stream is standard in, so it is
safe to do so.
This also requires us to change the logic first to open the file and then
check its status. The stat(2) is disallowed in capability mode.

This commit unbrakes the -F option.
The bug was introduced in the r348708.

Reported by: pho
Tested by: pho