sharness: Use sed in a cross-platform safe way
sharness: Use sed in a cross-platform safe way

OS X sed is documented as "-i SUFFIX", GNU sed as "-iSUFFIX". The one
consistent case seems to be "-iSUFFIX", where suffix cannot empty (or
OS X will parse the next argument as the suffix).

This used to leave around files named `refsout=` on Linux, and was
just confusing.

License: MIT
Signed-off-by: Jeromy <3e51041acc6532636d1f83f7ac2f8d6dab10a8ab@gmail.com>

OpenBazaar/go-ipfs,csasarak/go-ipfs,palkeo/go-ipfs,kyledrake/go-ipfs,bconfais/go-ipfs,rht/go-ipfs,Luzifer/go-ipfs,WilliButz/go-ipfs,WilliButz/go-ipfs,insionng/go-ipfs,tswindell/go-ipfs,kyledrake/go-ipfs,JustinDrake/go-ipfs,llawall/go-ipfs,ipfs-filestore/go-ipfs,JustinDrake/go-ipfs,RealImage/go-ipfs,kevina/go-ipfs,kevina/go-ipfs,kevina/go-ipfs,Kubuxu/go-ipfs,MichaelMure/go-ipfs,kpcyrd/go-ipfs,MrSparc/go-ipfs,shadoxx/go-ipfs,peersafe/go-ipfs,insionng/go-ipfs,shadoxx/go-ipfs,bconfais/go-ipfs,OpenBazaar/go-ipfs,palkeo/go-ipfs,bconfais/go-ipfs,kpcyrd/go-ipfs,palkeo/go-ipfs,Luzifer/go-ipfs,peersafe/go-ipfs,thelinuxkid/go-ipfs,chriscool/go-ipfs,thelinuxkid/go-ipfs,ianopolous/go-ipfs,MichaelMure/go-ipfs,shadoxx/go-ipfs,tswindell/go-ipfs,Kubuxu/go-ipfs,peersafe/go-ipfs,insionng/go-ipfs,WilliButz/go-ipfs,ianopolous/go-ipfs,llawall/go-ipfs,MrSparc/go-ipfs,JustinDrake/go-ipfs,llawall/go-ipfs,thelinuxkid/go-ipfs,chriscool/go-ipfs,chriscool/go-ipfs,Quantomicus/go-ipfs,kyledrake/go-ipfs,MichaelMure/go-ipfs,rht/go-ipfs,Luzifer/go-ipfs,csasarak/go-ipfs,MrSparc/go-ipfs,Quantomicus/go-ipfs,RealImage/go-ipfs,OpenBazaar/go-ipfs,RealImage/go-ipfs,Kubuxu/go-ipfs,tswindell/go-ipfs,ipfs-filestore/go-ipfs,kpcyrd/go-ipfs,Quantomicus/go-ipfs,csasarak/go-ipfs,ianopolous/go-ipfs,rht/go-ipfs,ipfs-filestore/go-ipfs