Fix: Remove duplicate stop capture message from handler queue

The removeMessages() method was incorrectly use == for comparing interface name strings,
which checks for the same object instance rather than content equality.
This could lead to duplicate stop capture messages remaining in the hanlder queue.
This change replaces removeMessages() with removeEqualMessages(),
which uses the equals() method to correctly compare the content of interface name strings,
and ensure duplicate stop capture messages are properly removed.

Bug: 406570694
Flag: EXEMPT bugfix
Test: atest NetworkStackTests
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:6f5cad80b55c2c5748969cd62382ac56512f0da2)
Merged-In: I4a61f8d2b693cd614b2083497639cc4262334746
Change-Id: I4a61f8d2b693cd614b2083497639cc4262334746