dumpstate: use pretty uptime, now in ABT

I was having a hard time reading this. Now it looks
like this:

------ UPTIME (uptime -p) ------
up 0 weeks, 0 days, 0 hours, 3 minutes,  load average: 37.75, 10.12, 3.55

Previously, it was like this, which is ambiguous:

08:35:37 up 16:07, 0 users, load average: 7.12, 11.39, 11.27

Yes, we lose the 'current time'. However, we also have this in the
bugreport a lot.

Fixes: 419080594
Test: adb bugreport (text above)

Change-Id: I26833a0d3e0e6b82a6dccda4b335006462c239b3