Check for server attributes before using them

Sets server attributes only after verifying that
they exist.

Risk of fix: With this fix the server.host, server.local_id,
server.deleted, server.deleted_at values could get set with
values from information loaded per
client.servers.get(instance.server_id). See bug notes for
more details

Change-Id: I6d8303fee0ab685bdbe66b044174a7bd9f0807a4
Closes-Bug:1376525
Merge "Check for server attributes before using them"