Update blobstore.conf.erb

client_max_body_size is hard-coded to 1GB which will cause uploading any release with size bigger than that failing. it should be configurable as that in bosh/release/director/templates/nginx.conf.erb.
Update spec
bump blobstore.max_upload_size to 5G

Signed-off-by: dmitriy kalinin <dmitriy@pivotallabs.com>