Change getUid before turning screen off

getUid is based on ADB shell command execution and device should be connected
to host. However, there're turnScreenOff during test and it causes device
getting suspend state. In that case, the test cannot complete properly due to
ADB disconnection. Therefore, getUid should be uppper turnScreenOff.

Bug: b/143046081
Test: run cts -m CtsStatsdHostTestCases -t android.cts.statsd.validation.ValidationTests#testPartialWakelockDuration
Change-Id: Id71f08d067d463e78a9dccb6b55dfab6c768888b
Merged-In: Id71f08d067d463e78a9dccb6b55dfab6c768888b