optionally allow a tolerance when checking script files

[bugfood]

This addresses:
#228
...without being a complete "fix", since that does not seem to be
possible.

Further details are in the bug report above, but in brief, Linux can
only report process start time with a precision of 1.1 seconds, and that
gets rounded off, thus false positives are quite possible for processes
that start immediately after their files are created.

Since this can allow some false negatives, allow the user to decide.
The default tolerance of 0 is no change from the previous behavior of
having no tolerance.

[bugfood]

I don't know if I accounted for all potential uses of the tolerance value; the only check I could find that uses process start time is the script check.

Before (or after with tolerance unspecified):

# PERL5LIB=perl/lib ./needrestart -plk
WARN - Kernel: <redacted>, Services: 1 (!), Containers: none, Sessions: none|Kernel=0;0;;0;2 Services=1;;0;0 Containers=0;;0;0 Sessions=0;0;;0
Services:
- <redacted>.service

After, with tolerance specified:

# PERL5LIB=perl/lib ./needrestart -plk -t 2
OK - Kernel: <redacted>, Services: none, Containers: none, Sessions: none|Kernel=0;0;;0;2 Services=0;;0;0 Containers=0;;0;0 Sessions=0;0;;0

Thanks,
Corey

[liske]

Thanks for your contribution!

[bugfood]

You're welcome, and thank you.