Add functions to handle idle maintenance

runIdleMaint is equivalent with:

1. echo 1 > /sys/fs/f2fs/sdX/gc_urgent
2. wait until /sys/fs/f2fs/sdX/dirty_segments
     <= threshold or timeout
3. echo 0 > /sys/fs/f2fs/sdX/gc_urgent
4. fstrim

abortIdleMaint forces the wait loop above to exit and
skips fstrim. However, if fstrim is already running,
abortIdleMaint will just leave it run to completion.

Test: adb shell sm idle-maint [run|abort]
Bug: 67776637
Change-Id: I4adff8d9b6bbd63bce41368cea55dc9e9b117eb6
diff --git a/model/PrivateVolume.h b/model/PrivateVolume.h
index 95b718d..9508671 100644
--- a/model/PrivateVolume.h
+++ b/model/PrivateVolume.h
@@ -39,6 +39,8 @@
 public:
     PrivateVolume(dev_t device, const std::string& keyRaw);
     virtual ~PrivateVolume();
+    const std::string& getFsType() { return mFsType; };
+    const std::string& getRawDevPath() { return mRawDevPath; };
 
 protected:
     status_t doCreate() override;