Only initialize SharkEnv once for unit tests.
Only initialize SharkEnv once for unit tests.

sjyk/sampleclean,sameeragarwal/blinkdb,mattyb149/blinkdb,sameeragarwal/blinkdb_dev,vax11780/shark,sjyk/sampleclean,mattyb149/blinkdb,alabid/blinkdb,vax11780/shark,sjyk/sampleclean,lzshlzsh/shark,amplab/shark,sameeragarwal/blinkdb_dev,sameeragarwal/blinkdb,sameeragarwal/blinkdb_dev,vax11780/shark,alabid/blinkdb,amplab/shark,mapr/shark,mattyb149/blinkdb,mapr/shark,sameeragarwal/blinkdb,alabid/blinkdb,lzshlzsh/shark,amplab/shark,mapr/shark,lzshlzsh/shark