lxd/network/driver/common: Ban : char from network names in ValidateName()
lxd/network/driver/common: Ban : char from network names in ValidateName()

This prevents network names from conflicting with vlan alias interface names and when used as a prefix for `restricted.networks.subnets` in projects.

Signed-off-by: Thomas Parrott <6b778ce645fb0e3dde76d79eccad490955b1ae74@canonical.com>

stgraber/lxd,lxc/lxd,stgraber/lxd,atxwebs/lxd,stgraber/lxd,lxc/lxd,lxc/lxd,lxc/lxd,stgraber/lxd,stgraber/lxd,stgraber/lxd,lxc/lxd,atxwebs/lxd,hallyn/lxd,hallyn/lxd,atxwebs/lxd,hallyn/lxd,lxc/lxd,lxc/lxd,hallyn/lxd,atxwebs/lxd,stgraber/lxd,hallyn/lxd,hallyn/lxd