vold: do not set gc sleep time with zero dirty segments am: 0b5f397e am: f605ac32

Original change: https://android-review.googlesource.com/c/platform/system/vold/+/2033123



Change-Id: I8c2ba8b86059a78b65094aa013e249c80f901a7f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>