logd: remove start filtration from flushTo

We have already searched for the start point, the start filter check
is paranoia that removes out-of-order entries that we are undoubtably
interested in.  Out-of-order entries occur under reader pressure, as
the writer gets pushed back from in-place sorted order and lands it
at the end for the reader to pick it up.  If this occurred during a
batch run or a logger thread wakeup, the entry could be filtered out
and never output to the reader.

Found one case where logcat.tail_time* tests failed which was fixed
with this adjustment.

Test: gTest logd-unit-tests, liblog-unit-tests and logcat-unit-tests
Bug: 38046067
Bug: 37791296
Change-Id: Icbde6b33dca7ab98348c3a872793aeef3997d460