build/mngids.py: fix groupname or username in uncommon position
build/mngids.py: fix groupname or username in uncommon position

adduser or addgroup can handle username or groupname at any
place as argument. This patch handle such cases.

For instance in the preinst script of the puppet package for
centos 7 there is such a call : groupadd -r puppet -g 52
where puppet is neither the first or the last argument.

redhat-cip/edeploy,enovance/edeploy,lebauce/edeploy,enovance/edeploy,enovance/edeploy,redhat-cip/edeploy,redhat-cip/edeploy,lebauce/edeploy,redhat-cip/edeploy,enovance/edeploy,lebauce/edeploy,lebauce/edeploy