Don't display bugreport progress when it recedes.

Also fixed InvalidNumberArgs that broke when usage() was moved out from
bugreport.cpp.

Fixes: 26354314
Bug: 28054087
Test: m -j32 adb_test && ./out/host/linux-x86/nativetest64/adb_test/adb_test --gtest_filter=BugreportTest.*

Change-Id: I7be5ef7de0fb0d339dc80a2abc816e1c905deb22