fix typo: sonartype -> Sonatype
Refactor the Translog.read(Location) method

It was only used by `readSource`, it has been changed to return a
Translog.Operation, which can have .getSource() called on it to return
the source. `readSource` has been removed.

This also removes the checked IOException, any exception thrown is
unexpected and should throw a runtime exception.

Moves the ReleasableBytesStreamOutput allocation into the body of the
try-catch block so the lock can be released in the event of an exception
during allocation.
Discovery: master fault detection fall back to cluster state thread upon error

With #7834, we simplified ZenDiscovery by making it use the current cluster state for all it's decision. This had the side effect a node may start it's Master FD before the master  has fully processed that cluster state update that adds that node (or elects the master master). This is due to the fact that master FD is started when a node receives a cluster state from the master but the master it self may still be publishing to other node.

This commit makes sure that a master FD ping is only failed once we know that there is no current cluster state update in progress.

Closes #7908
MLT Query: use minimum should match more extensive syntax

The minimum number of optional should clauses of the generated query to match
can now be set using the more extensive minimum should match syntax. This
makes the `percent_terms_to_match` parameter deprecated, and replaced in favor
to a new `minimum_should_match` parameter.

Closes #7898
Test: testNodeNotReachableFromMaster had a typo when choosing a non master node