vold: add gc period in setGCUrgentPace

To make gc period changable, added a new gcPeriod parameter to
setGCUrgentPace.

Test: adb shell device_config put storage_native_boot smart_idle_maint_period 10
Bug: 202283480
Bug: 181079477
Signed-off-by: Daeho Jeong <daehojeong@google.com>
Change-Id: I4e44a80ea5b51d9a7cde69d25e129dd0673b271f