libsnapshot: Quell error spam during factory data resets.

QuerySnapshotStatus assumes IsSnapshotDevice() would return true.

Additionally, recovery does not have access to /dev/loop-control, which
cannot be used by libfiemap anyway. Access it on-demand instead of
preemptively.

Bug: N/A
Test: manual test
Change-Id: I0f746870d7a8ec6d666f0bdd2fef3464b214928b

fs_mgr/libfiemap/image_manager.cpp

@@ -16,6 +16,8 @@
 
 #include <libfiemap/image_manager.h>
 
+#include <optional>
+
 #include <android-base/file.h>
 #include <android-base/logging.h>
 #include <android-base/properties.h>
@@ -574,7 +576,7 @@ bool ImageManager::UnmapImageDevice(const std::string& name, bool force) {
         return false;
     }
     auto& dm = DeviceMapper::Instance();
-    LoopControl loop;
+    std::optional<LoopControl> loop;
 
     std::string status;
     auto status_file = GetStatusFilePath(name);
@@ -598,9 +600,14 @@ bool ImageManager::UnmapImageDevice(const std::string& name, bool force) {
                 return false;
             }
         } else if (pieces[0] == "loop") {
+            // Lazily connect to loop-control to avoid spurious errors in recovery.
+            if (!loop.has_value()) {
+                loop.emplace();
+            }
+
             // Failure to remove a loop device is not fatal, since we can still
             // remove the backing file if we want.
-            loop.Detach(pieces[1]);
+            loop->Detach(pieces[1]);
         } else {
             LOG(ERROR) << "Unknown status: " << pieces[0];
         }

fs_mgr/libsnapshot/snapshot.cpp

@@ -1692,6 +1692,7 @@ UpdateState SnapshotManager::GetUpdateState(double* progress) {
     for (const auto& snapshot : snapshots) {
         DmTargetSnapshot::Status current_status;
 
+        if (!IsSnapshotDevice(snapshot)) continue;
         if (!QuerySnapshotStatus(snapshot, nullptr, &current_status)) continue;
 
         fake_snapshots_status.sectors_allocated += current_status.sectors_allocated;