fixed function to be consistent with other functions in how it gets the dfs_cmd
fixed function to be consistent with other functions in how it gets the dfs_cmd

- and confirmed no files in the repo use the ${fs_cmd} naming

tvanila/test.bdutil,taragu/bdutil,dennishuo/bdutil,AngusDavis/bdutil,AngusDavis/bdutil,davidadamsphd/bdutil,GoogleCloudDataproc/bdutil,ravwojdyla/bdutil,qix/bdutil,nsabharwal/bdutil,edwardyoon/bdutil,gruter/bdutil,pmkc/bdutil,gruter/bdutil,mbrukman/bdutil,GoogleCloudDataproc/bdutil,mbrukman/bdutil,tvanila/test.bdutil,nsabharwal/bdutil,qix/bdutil,levyx/bdutil,seanorama/bdutil,pmkc/bdutil,stev-0/bdutil,ravwojdyla/bdutil,edwardyoon/bdutil,taragu/bdutil,seanorama/bdutil,stev-0/bdutil,semad/bdutil,davidadamsphd/bdutil,semad/bdutil,levyx/bdutil,mxm/bdutil,mxm/bdutil,dennishuo/bdutil