Fix a typo to correctly check if variable is empty OR < 3 in   spark_on_yarn_env.sh. ------------- Created by MOE: https://github.com/google/moe MOE_MIGRATED_REVID=103348114
Fix a typo to correctly check if variable is empty OR < 3 in
  spark_on_yarn_env.sh.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=103348114

levyx/bdutil,pmkc/bdutil,GoogleCloudDataproc/bdutil,mxm/bdutil,mbrukman/bdutil,semad/bdutil,levyx/bdutil,mxm/bdutil,mbrukman/bdutil,seanorama/bdutil,semad/bdutil,dennishuo/bdutil,seanorama/bdutil,pmkc/bdutil,dennishuo/bdutil,GoogleCloudDataproc/bdutil