bgpd: Fix bgp clear help string

bgpd: Fix bgp clear help string

The bgp clear help string was misordered.

New output:
robot.cumulusnetworks.com# clear bgp
  (1-4294967295)  Clear peers with the AS number
  *               Clear all peers
  A.B.C.D         BGP neighbor address to clear
  WORD            BGP neighbor on interface to clear
  X:X::X:X        BGP IPv6 neighbor to clear
  external        Clear all external peers
  ipv4            Address Family
  ipv6            Address Family
  peer-group      Clear all members of peer-group
  prefix          Clear bestpath and re-advertise
  view            BGP view
  vrf             BGP VRF

Fixes: #1005
Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>