Fix admin user creation

[ro-ket]

Corrects syntax errors in the zone check and in the user assignment.

Fixes #6

Tests:

roket-admin-1# isi zone create --name z1 --create-path --path /ifs/z1
roket-admin-1# bash ~/isilon_create_users.sh --dist hwx --zone z1
Info: Hadoop distribution:  hwx
Info: will put users in zone:  z1
Info: HDFS root:  /ifs/z1
Info: passwd file: z1.passwd
Info: group file: z1.group
SUCCESS -- Hadoop users created successfully!
roket-admin-1# bash ~/isilon_create_users.sh --dist hwx --zone System
Info: Hadoop distribution:  hwx
Info: will put users in zone:  System
Info: HDFS root:  /ifs
Info: passwd file: System.passwd
Info: group file: System.group
SUCCESS -- Hadoop users created successfully!
Done!

Confirmed accounts, particularly admin account created properly in both zones. (admin account not created in System zone; already exists)