fix specs for rubygems >= 2.0.1
fix specs for rubygems >= 2.0.1

rubygems was trying to reference `FileUtils::Entry_` after we'd replaced
`FileUtils`. Delay the initial swap until `before(:suite)`.
ref: 4289f8259d56cb24a19cb72c13c68b0744bae1d1@7b03169c1e4f3efd16d63828a0e2315c488445d9

pollosp/backup,skcript/backup,zires/backup,skcript/backup,zires/backup,reedloden/backup,pollosp/backup,martincik/backup,McStork/backup,skcript/backup,backup/backup,bernd/backup,backup/backup,interu/backup,hiphapis/backup,rics3n/backup,otzy007/backup,hiphapis/backup,otzy007/backup,scalp42/backup,tian-xiaobo/backup,zBMNForks/backup,interu/backup,zBMNForks/backup,ccoenen/backup,zires/backup,scalp42/backup,rics3n/backup,pawelduda/backup,martincik/backup,backup/backup,pawelduda/backup,pollosp/backup,zBMNForks/backup,McStork/backup,scalp42/backup,ccoenen/backup,ccoenen/backup,tian-xiaobo/backup,otzy007/backup,martincik/backup,McStork/backup,interu/backup,tian-xiaobo/backup,pawelduda/backup,bernd/backup,reedloden/backup,hiphapis/backup,reedloden/backup,rics3n/backup