nostromo: make sure usr/group www-data exist
nostromo: make sure usr/group www-data exist

CQID: 422203

nostromo runs as user/group www-data and needs these
to exist when we install it.

Signed-off-by: Joe Slater <4672364201a76552c192fe79745f557138313c8c@windriver.com>

WindRiver-OpenSourceLabs/meta-webserver