Don't assume an A/B device when overriding the super partition name.

Bug: 130750333
Test: launch cuttlefish with DAP enabled
Change-Id: I1ea309d448866a8914f58be98d860eca36d47062

fs_mgr/fs_mgr.cpp

diff --git a/fs_mgr/fs_mgr.cpp b/fs_mgr/fs_mgr.cpp
index 5114f55..c1aafda 100644
--- a/fs_mgr/fs_mgr.cpp
+++ b/fs_mgr/fs_mgr.cpp
@@ -1695,11 +1695,12 @@
 
 std::string fs_mgr_get_super_partition_name(int slot) {
     // Devices upgrading to dynamic partitions are allowed to specify a super
-    // partition name, assumed to be A/B (non-A/B retrofit is not supported).
-    // For devices launching with dynamic partition support, the partition
-    // name must be "super".
+    // partition name. This includes cuttlefish, which is a non-A/B device.
     std::string super_partition;
     if (fs_mgr_get_boot_config_from_kernel_cmdline("super_partition", &super_partition)) {
+        if (fs_mgr_get_slot_suffix().empty()) {
+            return super_partition;
+        }
         std::string suffix;
         if (slot == 0) {
             suffix = "_a";