[mythtv] Possible bug when using override with postroll

[Bruce Markey]

Overrides don't seem to take effect if per-show preroll or
postroll are set. If I choose "Don't record it" on any showing
of a show that has postroll time, the conflicts page still shows
it as marked to record. However, if I go to the advanced options
page and set the *roll time to 0 then choose "Don't record it"
it will be marked correctly as nrManualOverride.

This is true if either pre or post time is set and for changing
state to 'do record' or to 'don't record'. Once the override
state is set, it appears that the state is preserved when the
roll times are changed but the state can't be changed unless
the roll times are zero.

--  bjm