If Ping encounters an error, wait before repinging.

This is a short-term fix; we should implement smarter backoff
behavior later. However, let's fix the battery burn immediately.

This CL also includes a fix to re-pinging in the error case for
people who do not have mail sync enabled.

Bug: 12589402
Bug: 13227663
Change-Id: If61d4a42fe846d8f4b5c16e84d6196ad61ddbe0e
2 files changed