edsp: try harder to not generate unneeded error messages
The &= introduced in the EDSP-FileFd conversion isn't working to full
satisfaction for multiple && clauses as the && has a higher binding than
&= has, so that the methods were called even through they shouldn't
have because of previous errors. Using variadic functions we can solve
this in a slightly cleaner way bringing down the amount of 'broken pipe'
errors for the error case of the dump resolver substantially.