Fix failure in regmatch^%ydbposixtest due to extraneous match results (regression in 9007dec8)
v60001/gtm_posix subtest in the YDBTest repo failed after commit 9007dec8 with the following diff.
> FAIL regmatch^%ydbposix 4 > FAIL REGMATCH^%ydbposix 4
This is because that commit erroneously assumed that
matchresults(i,"start") might not be set in the
for loop in case
$&ydbposix.regofft2offsets returned a non-zero value. And because of this, it added
$data(matchresults(i,"start")) check instead of the pre-existing
$&ydbposix.regofft2offsets always returns a 0. Therefore, the
$data check is not
necessary and in fact incorrect since we need to actually check for 0 value of
to terminate the for loop. This is now done. And comments added in the code to help a future reader.