remove cfd->options() in DBImpl::NotifyOnFlushCompleted

Summary: We should not reference cfd->options() directly!

Test Plan: make release

Reviewers: sdong, rven, igor, yhchiang

Reviewed By: igor, yhchiang

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D29061
remove all remaining references to cfd->options()

Summary:
The very last reference happens in DBImpl::GetOptions()
I built with both DBImpl::GetOptions() and ColumnFamilyData::options() commented out

Test Plan: make all check

Reviewers: sdong, yhchiang, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D29073