P2P: Clear p2p_in_invitation on cancel

P2P: Clear p2p_in_invitation on cancel

Commit 41d5ce9e0b7b37dd84fbf3c1aa5ed571c32321d4 added scan optimizations
for P2P invitation cases. However, it left a path where the invitation
state was not cleared and as such, introduced potential issues for
following scans that ended up getting incorrectly optimized for a single
channel regardless of parameters. Fix this by clearing p2p_in_invitation
more carefully, especially on p2p_cancel command.

p2p_cancel is now also run from the FLUSH command to avoid issues with
hwsim test cases (e.g., persistent_group_per_sta_psk followed by
ap_open_tdls resulted in an error due to p2p_in_invitation remaining set
after FLUSH).

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>