[Test] Let SuggestStatsTests.testSimpleStats do more work

The test verifies that stats are measure by checking timeInMillis>0. On fast machines the suggestions are done in < 1 millis time. The tests now index documents (to power suggestions) and does multiple suggestions per iterations to slow things down.
[DOCS] fix typo
Update function-score-query.asciidoc
[Tests] SimpleRecoveryLocalGatewayTests.testSingleNodeNoFlush could fail if shards were not started

The test starts a single node, indexes into, restarts the node and checks that no data was lost. It only indexed into 2 shards and didn't wait for green meaning that the node could be restarted with non-started primary. In that case the node will not re-assign the primary as it was not started. This commit makes sure that we either wait for primaries to start or index into all shards which has the same net effect.

Also extending some logging in InternalIndexShard.
Searcher might not be closed if store hande can't be obtained

Today we first get a reference to the IndexSearcher in #acquireSearcher
and then futher down we try to run Store#incRef() which might throw an
exception if the store is already closed. There is a small window
that allows this to happen during InternalEngine#close() when we try
to acquire the searcher at the same time and the engine is the last
resource that holds a reference to the store.

This commit only affects unreleased code since the Store's ref counting
has not yet been released.