docfix for vsphere_guest.py

Corrected parameter name from user to username in documentation
docfix for vsphere_guest.py

Corrected parameter name from user to username in documentation
Merge branch 'docfix' of github.com:IndyMichaelB/ansible-modules-core into docfix
Merge pull request #259 from IndyMichaelB/docfix

docfix for vsphere_guest.py