regression in flushinteval, module omfile, version 8.26

[grzsmp]

Last upgrade from 8.22 to 8.26 introduce regression in flushinterval parameter, which stop working.
Example configuration, which worked before upgrade:
$OMFileASyncWriting On
$OMFileFlushInterval 10
$OMFileFlushOnTXEnd off
$OMFileIOBufferSize 65536