Fix StorageManagerTest#testOpenProxyFileDescriptor*

Previously the test uses an override of openProxyFileDescriptor API
which does not take Handler and is hidden.

The CL updates the test so that it uses public verison which takes
Handelr.

Bug: 77605926
Test: atest StorageManagerTest
Change-Id: Id2cca9aeac789822a6f6ffb219838b2440d0452e
1 file changed