Fix trivial warnings in Tethering.java

( cherry-pick of 6d475970a200f162ba6845d25bb2a777bcaa611c )

Add some missing @Override annotations.
Use template arguments to avoid explicit casting.
Ignore unclosed IndentingPrintWriter in dump().

Bug: 28798823
Test: Compiles.

Change-Id: I2cb6eb384ca23057c8059f4842b1c0d8248d03f8
1 file changed