Fix captive portal can't show certificate problem

Captive portal overrides two shouldOverrideUrlLoading methods,
but show certificate logic only be implemented in deprecated one.

Bug: 133714666
Test: -build, flash, boot
      -atest FramworksNetTests
      -manual test

Change-Id: I2656bb709cb0bf259279ca75ad8411cd8c92fb43
Merged-In: I64b05adcb46baf3fca116dbdc5177bc31c71e06d
(cherry picked from commit 9161b5e8)