Description:
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fpm log prefix message includes wrong stdout/stderr notation

Test script:
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<?php
file_put_contents('php://stdout', "msg 1 - ");
usleep(1);
file_put_contents('php://stderr', "msg 2 - ");
usleep(1);
file_put_contents('php://stderr', "msg 3");

Expected result:
----------------
LOG LINE: [25-Jul-2019 23:34:52] WARNING: [pool unconfined] child 87539 said into stdout: "msg 1 - "
LOG LINE: [25-Jul-2019 23:34:52] WARNING: [pool unconfined] child 87539 said into stderr: "msg 2 - msg 3"


Actual result:
--------------
LOG LINE: [25-Jul-2019 23:34:52] WARNING: [pool unconfined] child 87539 said into stdout: "msg 1 - msg 2 - msg 3"