Force save profiles for SIGUSR1

Force save profiles from signal catcher for SIGUSR1. Saving the
profiles is expensive but we already do a GC which is also expensive
for this signal.

Test: adb shell ls -l /data/misc/profiles/cur/1000/system_server/
Test: adb shell kill -s SIGUSR1 `pid system_server`
Test: adb shell ls -l /data/misc/profiles/cur/1000/system_server/

Bug: 36457259
Bug: 34927277
Change-Id: I1852bba1a7f47b378ba0321edf951bca942b3c39