Really fix support for soname in apk.

Bug: 29218999

Test: Run a stack through vendor/google/tools/stack --auto with this change.
Change-Id: I0d650f30d37bb0dfa9db011d7624c0c74a98f2df
diff --git a/scripts/stack_core.py b/scripts/stack_core.py
index ed45618..452d83b 100755
--- a/scripts/stack_core.py
+++ b/scripts/stack_core.py
@@ -377,7 +377,7 @@
             index = area.rfind(".apk!")
             if index != -1:
               apk = area[0:index + 4]
-          if not apk:
+          if apk:
             lib_name, lib = self.GetLibFromApk(apk, so_offset)
         if not lib:
           lib = area