test: load libaio.so instead of libaio.so.1

[wenningerk]

as that is rather what sbd would link against without preloading on distros linking different library versions under these 2 names

[fabbione]

retest this please

[wenningerk]

It is still a bit unclear why access to the original functions from the preload-wrapper doesn't work via RTLD_NEXT as with everything else.
Still investigating this and if there is no way around explicitly loading the library it might make sense to record at build time which library the linker had seen.
Well it is 'just' for test purposes - and thus this minimal change for now to make debian-testing & experimental happy that do see different libraries via libaio.so and libaio.so.1 atm.