Remove extra handler#post inside setIncludeTestInterfaces

This was (mistakenly?) added in aosp/1267639 patchset 2; however, there
does not seem to be any apparent reason to post
trackAvailableInterfaces() to the back of the handler thread. All
operations that precede trackAvailableInterfaces() are synchronous.

Test: atest EthernetManagerTest
Change-Id: Ic8e888ce5d8909c4b7a00e26c54286c454ff3e75
1 file changed