allow micro bosh to set agent ntp servers

- refactored settings into its own class

Change-Id: I9dc67107f0739e8750e5d9588abaee57aedf6e6e
add set_vm_metadata to aws cpi

Change-Id: I946b9d44e2c366dafc970e01b07bb02174700c39
Merge "allow micro bosh to set agent ntp servers"
Merge "add set_vm_metadata to aws cpi"