Fix unit tests errors

Summary: Those were introduced with https://github.com/facebook/rocksdb/commit/2fb1fea30fd027bbd824a26b682d04d91a8661dc because the flushing behavior changed when max_background_flushes is > 0.

Test Plan: make check

Reviewers: ljin, yhchiang, sdong

Reviewed By: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D23577
[Java] Fix JNI link error caused by the removal of options.db_stats_log_interval

Summary: Fix JNI link error caused by the removal of options.db_stats_log_interval in https://reviews.facebook.net/D21915.

Test Plan:
make rocksdbjava
make jtest

Reviewers: ljin, ankgup87

Reviewed By: ankgup87

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D23505
Fix build
Merge pull request #299 from ankgup87/master

[Java] Fix build
RocksDB: Format uint64 using PRIu64 in db_impl.cc

Summary: Use PRIu64 to format uint64 in a portable manner

Test Plan: Run "make all check"

Reviewers: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D23595