hil: ota: wait for firmware update state to propagate

[hasheddan]

Introduces a short wait (2 seconds) for firmware update state changes to propagate. State changes are not guaranteed to be immediately reflected for a device after an OK response is received.

In the future, this stop-gap solution should be replaced by either polling in this test or synchronous behavior on the server. Currently the on-device test is waiting 7s between state updates, so the wait in this test must remain less than to avoid missing a state update.

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Code Coverage

Type	Coverage
lines	57.3% (1275 of 2225 lines)
functions	65.3% (126 of 193 functions)