tests: Fix ap_ft_r0_key_expiration test

tests: Fix ap_ft_r0_key_expiration test

The test configures ft_r0_key_lifetime parameter, however ft_params
already contain the r0_key_lifetime. Since both options are accepted by
hostapd and set the same field, one of them gets overwritten.
As the dictionary enumeration order is not guaranteed in python, the
test may sporadically fail.
Fix that by explicitely removing the unneeded parameter.

Signed-off-by: Andrei Otcheretianski <andrei.otcheretianski@intel.com>