HS 2.0: Do not add two copies of OSEN element into Beacon/Probe Resp

HS 2.0: Do not add two copies of OSEN element into Beacon/Probe Resp

OSEN element was getting added both through the Authenticator IEs
(before some non-vendor elements) and separately at the end of the
frames with other vendor elements. Fix this by removing the separate
addition of the OSEN element and by moving the Authenticator IE addition
for OSEN to match the design used with WPA so that the vendor element
gets added in the proper place in the sequence of IEs.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>