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

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



Change-Id: I30d462858c6b3acc8e7aebc9bed55deb4716db14
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>