Removed `O_SYNC` from StatusUpdateManager.
Removed `O_SYNC` from StatusUpdateManager.

The StatusUpdateManager data is not recovered after reboot. This means
we can rely on flushes to the page cache to be sufficient for writing
status updates.

Review: https://reviews.apache.org/r/50635/

kaysoky/mesos,chhsia0/mesos,reneploetz/mesos,dforsyth/mesos,andschwa/mesos,gsantovena/mesos,asamerh4/mesos,abudnik/mesos,asamerh4/mesos,chhsia0/mesos,verizonlabs/mesos,gsantovena/mesos,dforsyth/mesos,Aman-Jain-14/customizedMesos,kaysoky/mesos,craimbert/mesos,zmalik/mesos,reneploetz/mesos,Aman-Jain-14/customizedMesos,abudnik/mesos,neilconway/mesos,abudnik/mesos,dforsyth/mesos,verizonlabs/mesos,asamerh4/mesos,Gilbert88/mesos,yuquanshan/customizedMesos,reneploetz/mesos,verizonlabs/mesos,jpeach/mesos,jpeach/mesos,verizonlabs/mesos,dforsyth/mesos,andschwa/mesos,jpeach/mesos,kaysoky/mesos,yuquanshan/customizedMesos,Aman-Jain-14/customizedMesos,verizonlabs/mesos,andschwa/mesos,Gilbert88/mesos,jpeach/mesos,zmalik/mesos,asamerh4/mesos,craimbert/mesos,neilconway/mesos,craimbert/mesos,Gilbert88/mesos,yuquanshan/customizedMesos,neilconway/mesos,kaysoky/mesos,neilconway/mesos,chhsia0/mesos,andschwa/mesos,chhsia0/mesos,reneploetz/mesos,gsantovena/mesos,kaysoky/mesos,dforsyth/mesos,kaysoky/mesos,dforsyth/mesos,chhsia0/mesos,neilconway/mesos,gsantovena/mesos,verizonlabs/mesos,andschwa/mesos,Gilbert88/mesos,reneploetz/mesos,gsantovena/mesos,gsantovena/mesos,chhsia0/mesos,chhsia0/mesos,asamerh4/mesos,zmalik/mesos,andschwa/mesos,craimbert/mesos,yuquanshan/customizedMesos,gsantovena/mesos,reneploetz/mesos,kaysoky/mesos,yuquanshan/customizedMesos,verizonlabs/mesos,abudnik/mesos,zmalik/mesos,abudnik/mesos,yuquanshan/customizedMesos,neilconway/mesos,craimbert/mesos,Gilbert88/mesos,Gilbert88/mesos,craimbert/mesos,jpeach/mesos,Aman-Jain-14/customizedMesos,dforsyth/mesos,Aman-Jain-14/customizedMesos,zmalik/mesos,Aman-Jain-14/customizedMesos,abudnik/mesos,Aman-Jain-14/customizedMesos,andschwa/mesos,asamerh4/mesos,abudnik/mesos,zmalik/mesos,jpeach/mesos,zmalik/mesos,yuquanshan/customizedMesos,craimbert/mesos,asamerh4/mesos,jpeach/mesos,Gilbert88/mesos,neilconway/mesos,reneploetz/mesos