Fix user existence detection
Fix user existence detection

cf create-user output if user already exists is send to stderr so it was never present in ${TMP_OUTPUT} so the condition to check for error always passed.

alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf