Fix TestRollingFileWithoutDeleteAppender test case testFileNamePattern

The log size is set to 10 bytes. However if the message size is 15 bytes, it creates a 15, 15 and 0 byte file ( which is sometimes flaky)

Explanation:
Before we logged a string that was at 15 bytes each. The assumption was Logger would split that across 2 files but it never did that. It would put 15 bytes of line on one file.

Previously we had 2 log statements:
debug."123456789012345";
debug."123456789012345";

The file being created was "123456789012345", "123456789012345", "" (LAST ONE empty)

as opposed to "1234567890", "1234512345", "6789012345"

The above output would be flaky because LOGGER.appender did not handle a LONG string properly. It would sometimes generate two files with "123456789012345", "" (LAST ONE empty)