cmd/import-rsnapshot: fix a bashism (== instead of =).
cmd/import-rsnapshot: fix a bashism (== instead of =).

Bug reported by Brandon Low.

Signed-off-by: Avery Pennarun <e03ccfb89d416c4697ad6970ce86a92c1c28a78e@gmail.com>

ToxicFrog/bup,ToxicFrog/bup,tjanez/bup,jbaber/bup,tjanez/bup,mhoeher/bup,pombredanne/bup,mhoeher/bup,ToxicFrog/bup,tjanez/bup,apenwarr/bup,apenwarr/bup,mhoeher/bup,gevaerts/bup,mhoeher/bup,apenwarr/bup,jbaber/bup,pombredanne/bup,gevaerts/bup,gevaerts/bup,jbaber/bup,pombredanne/bup,pombredanne/bup,mhoeher/bup,jbaber/bup,pombredanne/bup,apenwarr/bup,tjanez/bup,jbaber/bup,gevaerts/bup,jbaber/bup,mhoeher/bup,gevaerts/bup,tjanez/bup,pombredanne/bup,ToxicFrog/bup,ToxicFrog/bup,tjanez/bup