Summary:
In patch https://reviews.facebook.net/D47067, we change the
log level of the initial database information to header level.
As a result, even when the InfoLogLevel is set to Fatal, the
LOG file of a newly opened rocksdb instance will not be empty.
However, the current InfoLogLevelTest expect it should be empty.
This patch fixes this issue by enabling InfoLogLevelTest to
ignore the Log header.
Test Plan: make jtest
Reviewers: fyrz, anthony, IslamAbdelRahman, sdong, adamretter
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D47229
ff57c6511d