Support loading vdex files without odex.

GetDexoptNeeded with 'verify' as filter will return false when a vdex is
available.

Test: 628-vdex, 820-vdex-multidex, test.py
Bug: 176960283
Change-Id: I3ac2f747d1e7f5331a49a22c94983959e3b60122
diff --git a/test/820-vdex-multidex/expected-stdout.txt b/test/820-vdex-multidex/expected-stdout.txt
new file mode 100644
index 0000000..e965047
--- /dev/null
+++ b/test/820-vdex-multidex/expected-stdout.txt
@@ -0,0 +1 @@
+Hello