FLUME-1788: Flume Thrift source can fail intermittently because of a race condition in Thrift server implementation on some Linux systems

(Venkat Ranganathan via Brock Noland)
FLUME-1795: Flume thrift legacy source does not have proper logging configured

(Venkat Ranganathan via Brock Noland)
FLUME-1761. FileChannel can NPE when log metadata file is empty

(Brock Noland via Hari Shreedharan)
FLUME-1794. FileChannel check for full disks in the background

(Brock Noland via Hari Shreedharan)
FLUME-1789: Unit tests TestJCEFileKeyProvider and TestFileChannelEncryption fail with IBM JDK and flume-1.3.0

(Aline Guedes Pinto via Brock Noland)
FLUME-1810. Update CHANGELOG for Apache Flume-1.3.1 release.
FLUME-1811. Update RELEASE-NOTES for Flume 1.3.1
FLUME-1812. Update pom files for Flume 1.3.1 release
FLUME-1813. Update LICENSE file.
FLUME-1811. Update RELEASE-NOTES for Flume 1.3.1
FLUME-1810. Update CHANGELOG for Apache Flume 1.3.1
Add zabbix monitor
Merge branch 'release-1.3.1-mirror' into flume-1.3.1-dev