Premature optimization that tried to cache monitors but the cache did
not take into account the parameter values.
The call `get_monitors(..., ..., false, true);` would get all connected
and unconncected monitors a subsequent call
`get_monitors(..., ..., true, false);` would get back the same list of
monitors even though it requested only connected monitors.
Additionally `get_monitors` is never called periodically so the
optimization really didn't help much.
This adds `monitor-exact = true` in the bar section
This also properly does best-match instead of first-match if multiple
matches exists. For example if there are two monitors HDMI2 and HDMI-2
and we try to match HDMI-2 with monitor-exact = false, until now HDMI2
would be matched. Now exact matches are always preferred.
Fixes#1532
