I had 'similar' issues after the upgrade. Mine, however, were net limited to postfix only. The problem in my case was that eth0 was unable to initialize due to the kernel modules for the selected kernel not being available for the kernel that had been selected in the hypervision/droplet-panel. Yours might have the same issues (a module not being able to load, being loaded incorrectly).

Fix:

1. Check which versions of the kernel modules are installed: yum list --showduplicates kernel
2. Select one of the kernels shown in the droplet settings-page.
3. Shutdown your droplet using the console/ssh: shutdown -h now
4. Power-On using the control panel

Hope it helps you!

Not the requestor but this helped after my upgrade last night, thanks!!!

(Adding more as this is the only ticket with an answer I could find)
Note -- they list many many kernels in the droplet setting page, so don't get overwhelmed (as I was) when given so many choices. Just find what kernel(s) are installed on your system with the yum command above and match one via dropdown.

Also there was a delay to get a "Power On" button after I did a shutdown via command line (console). Be patient.