Replace all FIRST_SDK_INT usage in Connectivity because it has
been renamed to DEVICE_INITIAL_SDK_INT.
Bug: 184735771
Test: m CtsNetTestCases
Merged-In: I2f155592b08cdbf259a00b035cacb37ca9847e72
(clean cherry-pick)
Change-Id: I2f155592b08cdbf259a00b035cacb37ca9847e72