redhat: support vlan devices named as "vlan${TAG}"
    
    Since at least the version of initscripts that is in current
    RHEL6/CentOS6 (9.03.53) initscripts supports two different naming
    styles for vlan interfaces:
    
       $PHYSDEV.$TAG, e.g. "eth0.52"
       vlan$TAG, e.g. "vlan52"
    
    In the former case, both the physical device and the vlan tag are
    embedded in the vlan device name; in the latter case, only the vlan
    tag is embedded in the name, and initscripts (or NetworkManager) looks
    for the attribute PHYSDEV in the ifcfg file, and uses that as the
    physical device.
    
    netcf was originally written back in the days of RHEL5, and interfaces
    named "vlanXXX" weren't supported yet, so until now netcf has only
    recognized the old "eth0.42" style.
    
    This patch fixes that omission - existing vlan interfaces named
    "vlanXYZ" are now properly recognized, and new ones can be created.
    
    (NB: It is still odd that the digits at the end of the interface name
    must match the vlan tag, but there's unfortunately nothing that can be
    done about that, since there is no explicit variable in the ifcfg file
    that can be used to set the vlan tag.)
    
    Signed-off-by: Leno Hou <lenohou@gmail.com>