image: backends: Implement a cleanup() method

This allows backends to implement their own handling of target umounts.
Notably, the tar backend already umounts the target /dev /proc /sys, so
our hardcoded cleanup in the Creator caused unnecessary and confusing
error output when umount was run a second time.

Closes: #345

1 files changed, 6 insertions, 0 deletions

diff --git a/image/backends/tar.cc b/image/backends/tar.cc
index b05f4a5..a110acb 100644
--- a/image/backends/tar.cc
+++ b/image/backends/tar.cc
@@ -175,6 +175,12 @@ ret:
 
         return 0;
     }
+
+    void cleanup() override {
+        /* We call umount during creation to avoid including the dirs in the tarball,
+         * so we don't need the default cleanup to run. */
+        return;
+    }
 };
 
 __attribute__((constructor(400)))