FLUME-2323: Morphline sink must increment eventDrainAttemptCount when it takes event from channel

(Hari Shreedharan via Jarek Jarcec Cecho)
FLUME-2283: Spool Dir source must check interrupt flag before writing to channel

(Hari Shreedharan via Jarek Jarcec Cecho)
FLUME-2329: Add an alias for the Morphline Solr Sink

(Hari Shreedharan via Jarek Jarcec Cecho)