Rebuilding an instance on a RAIDed ESPs will fail due to sgdisk
running against an non-clean disk and bailing out. Check if there
is a RAIDed ESP already and skip creation if it exists.
Change-Id: I13617ae77515a9d34bc4bb3caf9fae73d5e4e578
(cherry picked from commit 286d66709a1b2f2068360db641079c67197b21b6)