Fix adouble refcounting

Fix adouble refcounting

Opening a file that doesn't have metadata with ADFLAGS_HF | AFFLAGS_NOHF
resulted in a successfull open (the error from the failed opening
of the nonexistent metadata is suppressed by AFFLAGS_NOHF), but
then the metadata refcount was increased becasue the error condition
was already reset to 0 at the place where we checked it.
Fixing this requires pushing the refcount increment deeper down the stack
into the individual functions where the error condition is still
available.

After fixing this, another bug became apparent in the mostyl empty
function ad_open_rf_v2().

Also fix an if check where what should be a comparison clobbered
a struct field.