Fix setResolverConfiguration to return negative error code

This fixes the logging bug in dumpsys netd.

For example, when resolv_set_nameservers fails:
It used to print
    setResolverConfiguration() -> ServiceSpecificException(-22, "Unknown error -22") <0.18ms>

After the fix, it prints
    setResolverConfiguration() -> ServiceSpecificException(22, "Invalid argument") <0.28ms>

Test: m com.android.resolv
Change-Id: I916e6e31dcdd2f421592e8ca71663ffbddc7b3b5