The code was not properly deciding if a lock needs to be removed
when it doesn't have quorum anymore. After this commit, a lock will be
forcefully unlocked if nodes reporting they are not able to find a lock
internally breaks the quorum.
Simplify the code as well.
also simplify readerLocks to be just like
writeLocks, DRWMutex() is never shared
and there are order guarantees that need
for such a thing to work for RLock's
This is to ensure that there are no projects
that try to import `minio/minio/pkg` into
their own repo. Any such common packages should
go to `https://github.com/minio/pkg`
