9a24ae88da
Currently only used by XenAPI. Sets GZIP environment variable before spawning tar -cz to force the compression level. Defaults to none, which means the GZIP environment variable is not set and the default (usually -6) is used. Implements: blueprint image-compression-mode Change-Id: I02e136b7215a4f2cefc259f40bde9c1b205737ed