thermal-hal: Evaluate severity for netlink sample event

Netlink Sample event and Violation event occurs back to back when a
threshold or hysteresis is violated or cleared. Since these events
happen in two separate threads, there is a possibility that violation
event gets executed before the sample event acquires the same mutex.
This will make the thermal severity estimation to evaluate based on the
old temperature data, since the sample event has not updated the
temperature yet.

To address the race condition, evaluate severity in the sample event
also. This will ensure that the severity is evaluated if the sample
event executes later.

Change-Id: I61fba0b07a700e0a0619d57a16d4b969e1feb57d