Refactor compute_api reboot tests to be unit-y

This follows previous efforts to unittest-ify the reboot
tests for compute_api. This makes the cells testing much
cleaner, and will massively simplify testing with objects.

Related to blueprint compute-api-objects

Change-Id: I5883f74c613888ed5f112ac1b7b1521f43644768
Make instance_update() string-convert IP addresses

Since postgres is strongly typed, it gets annoyed if we pass our
netaddr.IPAddress objects to it for an update. This makes the
instance_update() operation string-convert those before passing
them to the sqlalchemy save method.

Related to blueprint compute-api-objects

Change-Id: Ie9d4a59f50e59e80e88a8bb88575b89ce2e59091
Merge "Refactor compute_api reboot tests to be unit-y"
Merge "Make instance_update() string-convert IP addresses"
Merge remote-tracking branch 'm_src_repo/citrix-fixes' into build-temp