Better deal with invalid scroll ids.

Closes #5738
[TEST] Reduce the amount of docs being indexed.
add debug logs if failed shards can not be resolved.
Ensure close is called under lock in the case of an engine failure

Until today we did close the engine without aqcuireing the write lock
since most calls were still holding a read lock. This commit removes
the code that holds on to the readlock when failing the engine which
means we can simply call #close()
[TEST] catch exceptions if TTL already expired when indexing

TTLPercolatorTests indexes docs with small TTLs which can trigger
AlreadyExpiredException exception. This is expected while rare and
we should just catch them.
[TEST] Ignore bogus system properties.

LuceneTestCase might reset some solr properties that cause
our tests to fail if the run before in the same JVM We just ignore
solr properties.
Update multi-match-query.asciidoc

Typo
[Test] InternalEngineTests: increased gc deletes interval & turn it off randomly
Added version constants for 1.1.2 and 1.0.4
[TEST] make testTimeoutSendExceptionWithDelayedResponse more reliable on slow systems
[DOCS] Make snapshot repository examples consistent
[TEST] Use startNodesAsync in unicast discovery tests.
Update allocation.asciidoc
[BUILD] Fail release if test have AwaitsFix annotations

Note this commit upgrades Forbidden APIs to version 1.5

Closes #5807
Add a site plugin into list

Howdy,

Not sure if this is kosher but I would like to add my site plugin to the list in the docs.
[TEST] added sort by "_id" when score is the same to MultiMatchQueryTests#testEquivalence

A merge (and refresh) might rarely happen in the background between the two queries whose output is compared. It might then happen that two docs with same scores get returned by the two queries in a different order due to different lucene document id (which has changed in the meantime). To fix this we need to order by id when the score is the same, so that we can safely compare the output of the two queries (multimatch and dismax).
Moved the updateMappingOnMaster logic into a single place.

Closes #5798