Fix renew and revoke lease
Fix renew and revoke lease

According to vault API documentation the renew the lease_id should be include in the request body and not part of the URL.

This fix was original proposed in kr1sp1n/node-vault#52.

See:
https://www.vaultproject.io/api/system/leases.html#renew-lease
https://www.vaultproject.io/api/system/leases.html#revoke-lease
Aloomaio/node-vault,kr1sp1n/node-vault