interface-reconfigure: Various refactoring
interface-reconfigure: Various refactoring

Move functions around and rename to reduce diff with vswitch
version. (The vswitch version has previously had the function names
rationalised and functions reordered into functional groups).

- Move check_allowed() to new "Boot from Network filesystem or device."
  section. Add usage comment.
- Move interface_name() to new section "Bare Network Devices" and rename
  pif_netdev_name().
- Move interface_exists() to "Bare Network Devices" and rename netdev_exists().
- Move configure_static_routes() to "IP device configuration" and
  rename ipdev_configure_static_routes().
- Move configure_network() to "IP device configuration" and rename
  ipdev_configure_network().

Signed-off-by: Ian Campbell <9be92b3dbbd6611e3e4c9209fb3d04b4919e7cca@citrix.com>

guard163/xen-api,guard163/xen-api,cheng-z/xen-api,robertbreker/xen-api,djs55/xen-api,jjd27/xen-api,ravippandey/xen-api,ravippandey/xen-api,cheng--zhang/xen-api,simonjbeaumont/xen-api,djs55/xen-api,djs55/xen-api,salvocambria/xen-api,koushikcgit/xen-api,djs55/xen-api,srowe/xen-api,vasilenkomike/xen-api,huizh/xen-api,robertbreker/xen-api,Frezzle/xen-api,huizh/xen-api,thomassa/xen-api,djs55/xen-api,agimofcarmen/xen-api,robertbreker/xen-api,anoobs/xen-api,koushikcgit/xen-api,jjd27/xen-api,simonjbeaumont/xen-api,rafalmiel/xen-api,srowe/xen-api,ravippandey/xen-api,koushikcgit/xen-api,guard163/xen-api,anoobs/xen-api,cheng-z/xen-api,jjd27/xen-api,djs55/xen-api,simonjbeaumont/xen-api,vasilenkomike/xen-api,rafalmiel/xen-api,cheng--zhang/xen-api,thomassa/xen-api,robertbreker/xen-api,huizh/xen-api,Frezzle/xen-api,huizh/xen-api,salvocambria/xen-api,ravippandey/xen-api,jjd27/xen-api,cheng-z/xen-api,Frezzle/xen-api,salvocambria/xen-api,cheng-z/xen-api,simonjbeaumont/xen-api,agimofcarmen/xen-api,cheng--zhang/xen-api,huizh/xen-api,rafalmiel/xen-api,koushikcgit/xen-api,simonjbeaumont/xen-api,simonjbeaumont/xen-api,srowe/xen-api,anoobs/xen-api,cheng--zhang/xen-api,cheng--zhang/xen-api,cheng-z/xen-api,robertbreker/xen-api,rafalmiel/xen-api,thomassa/xen-api,anoobs/xen-api,ravippandey/xen-api,cheng-z/xen-api,thomassa/xen-api,jjd27/xen-api,agimofcarmen/xen-api,vasilenkomike/xen-api,salvocambria/xen-api,guard163/xen-api,koushikcgit/xen-api,cheng-z/xen-api,jjd27/xen-api,cheng--zhang/xen-api,rafalmiel/xen-api,salvocambria/xen-api,koushikcgit/xen-api,robertbreker/xen-api,anoobs/xen-api,cheng--zhang/xen-api,Frezzle/xen-api,vasilenkomike/xen-api,euanh/xen-api,guard163/xen-api,agimofcarmen/xen-api,euanh/xen-api,anoobs/xen-api,vasilenkomike/xen-api,vasilenkomike/xen-api,guard163/xen-api,agimofcarmen/xen-api,srowe/xen-api,euanh/xen-api,thomassa/xen-api,Frezzle/xen-api,thomassa/xen-api,ravippandey/xen-api,salvocambria/xen-api,euanh/xen-api,euanh/xen-api,euanh/xen-api,srowe/xen-api,rafalmiel/xen-api,huizh/xen-api,agimofcarmen/xen-api