Add help about the id 'auto' for flavor-create
Add help about the id 'auto' for flavor-create

The id parameter of 'nova flavor-create' can be specified 'auto' now.
But the help document is not mentioned about that. This patch fixes it.

Fixes bug 1112154

Change-Id: I6df71746a0036c6b6d05467e28343fad2972c128

guptaankita/python-novaclient,JioCloud/python-novaclient,takeshineshiro/python-novaclient,takeshineshiro/python-novaclient,metacloud/python-novaclient,Shihta/python-novaclient,guptaankita/python-novaclient,citrix-openstack-build/python-novaclient,akash1808/python-novaclient,mat128/python-novaclient,ntt-sic/python-novaclient,citrix-openstack-build/python-novaclient,Shihta/python-novaclient,CCI-MOC/python-novaclient,ntt-sic/python-novaclient,JioCloud/python-novaclient,CCI-MOC/python-novaclient,mat128/python-novaclient,akash1808/python-novaclient,metacloud/python-novaclient