mgr/dashboard: Bucket creation fails when selecting locking with certain values
Description of problem:
When creating a bucket (Object Gateway > Buckets > Create) and enabling
object locking, you're required to set days or years but not both.
When you set days and leave years field empty (or vice versa) you get an error.
Steps to Reproduce:
1. Object Gateway > Buckets > Create: fill required fields.
2. Locking > check "Enable"
3. leave years empty (blank field) and set integer in days (or vice versa)
4. Click on "Create Bucket".
500 - Internal Server Error
Bucket creation successful.