AP: Allow PTK rekeying without Ext KeyID to be disabled as a workaround

AP: Allow PTK rekeying without Ext KeyID to be disabled as a workaround

Rekeying a pairwise key using only keyid 0 (PTK0 rekey) has many broken
implementations and should be avoided when using or interacting with
one. The effects can be triggered by either end of the connection and
range from hardly noticeable disconnects over long connection freezes up
to leaking clear text MPDUs.

To allow affected users to mitigate the issues, add a new hostapd
configuration option "wpa_deny_ptk0_rekey" to replace all PTK0 rekeys
with disconnection. This requires the station to reassociate to get
connected again and as such, can result in connectivity issues as well.

Signed-off-by: Alexander Wetzel <alexander@wetzel-home.de>