releasetools: Use the first entry of a mount point when reading fstab

There may be multiple entries in fstab for a mount point. Use the first
value found so the entries are prioritized in order.

Change-Id: Ibd2631413d3e00507d3a0ec84fb91755f1c7993c
Ticket: OPO-326

tools/releasetools/common.py

@@ -1241,9 +1241,10 @@ def LoadRecoveryFSTab(read_helper, fstab_version, recovery_fstab_path):
         context = i
 
     mount_point = pieces[1]
-    d[mount_point] = Partition(mount_point=mount_point, fs_type=pieces[2],
-                               device=pieces[0], length=length, context=context,
-                               slotselect=slotselect)
+    if not d.get(mount_point):
+        d[mount_point] = Partition(mount_point=mount_point, fs_type=pieces[2],
+                                   device=pieces[0], length=length, context=context,
+                                   slotselect=slotselect)
 
   return d