User demouser while running examples in VM

If running column access example in vm in examples page, we should not get what we want. Because $USER (cloudera) also belongs to hive group which has db_creator role. And db_creator role have (server all) permission.

So we'd better run examples with the demouser. Since the latest VM already create demogroup and demouser for us, we do not need to create them in the examples.
remove Create a group named usergroup and Add the current user to the group

When running examples, we should use demouser, eg.
[cloudera@quickstart ~]$ sudo su demouser hadoop jar \
./recordservice-client-0.1/lib/recordservice-examples-0.1.jar \
com.cloudera.recordservice.examples.mapreduce.RecordCount \
"select lastname, salary from rs.employees" "/tmp/count_salary_output"

[cloudera@quickstart ~]$ sudo su demouser hadoop jar \
./recordservice-client-0.1/lib/recordservice-examples-0.1.jar \
com.cloudera.recordservice.examples.mapreduce.RecordCount \
"select firstname, lastname, phonenumber from rs.employees" \
"/tmp/count_phonelist_output"