Improve timeouts for ADB push. Fixes #1319.

It was timing out while the request was still in progress, on larger
transfers and slower devices. Now there is a 10-seconds-between-packets
timeout and a master 5 minute timeout for the whole HTTP transaction. No
timeout on the RSA key generation or signing, though, since the crypto
is so slow.
Merge pull request #1490 from shepheb/timeouts

Improve timeouts for ADB push. Fixes #1319.