User correct file name when roll-over based on size

[songdongsheng]

When I rolling by day, and use fileNamePattern have small unit than day, e.g. fileNamePattern is:

%d{yyyyMMdd}/logback-%d{yyyyMMdd_HHmmss, aux}.txt

Then the time part in the file name is fixed:

logback-20170723_234823-0.txt logback-20170723_234823-1.txt logback-20170723_234823-2.txt logback-20170723_234823-3.txt logback-20170723_234823-4.txt logback-20170723_234823-5.txt

This looks is ugly and wrongly.

[songdongsheng]

This patch can cherry-pick to 1.2.x