TAJO-1195: Remove unused CachedDNSResolver Class. (DaeMyung Kang via jaehwa)

Closes #253
TAJO-1197: Unit test failed: unable to create new native thread. (jinho)

Closes #255
TAJO-1200: Invalid shuffle data of multiple worker in same server. (jinho)

Closes #259
TAJO-1181: Avro schema URL should support various protocols. (jinho)

Closes #252