Remove android.net.PskKeyManager

android.net.PskKeyManager does not work with upcoming TLS 1.3.
The class does not appear to be used by any Android apps and is thus
likely to be completely removed in the future.

Bug: 30978706
Test: make && make cts
Change-Id: Id9bae20362c5909e4621cdb00102bfee09d970ec
7 files changed