Fix description of user creation in README
Fix description of user creation in README

rhcarvalho/mongodb,openshift/mongodb,omron93/mongodb,fheng/mongodb,hhorak/mongodb,sclorg/mongodb-container,omron93/mongodb-container,omron93/mongodb-container,bparees/mongodb,sclorg/mongodb-container,ivanthelad/mongodb,gabemontero/mongodb,mfojtik/mongodb,bparees/mongodb,fheng/mongodb,gabemontero/mongodb