Velero should handle cases when the label length exceeds 63 characters.
- if the length of the backup/restore name is <= 63 characters, use it as the value of the label
- if it's > 63 characters, take the SHA256 hash of the name. the value of
the label will be the first 57 characters of the backup/restore name
plus the first six characters of the SHA256 hash.
Fixes heptio#1021
Signed-off-by: Anshul Chandra <anshulc@vmware.com>