tests: Fix dfs_cac_restart_on_enable false negative by using common finalizer
dfs_cac_restart_on_enable fails with this message.
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START dfs_cac_restart_on_enable 1/1
wlan0: Country code not reset back to 00: is FI
wlan0: Country code cleared back to 00
FAIL dfs_cac_restart_on_enable 3.037694 2019-05-28 01:35:07.548390
failed tests: dfs_cac_restart_on_enable
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