isReservedSupported=true when running as container

Test: Remove first_sdk_check from StorageHostTest#testVerify, log
Build.IS_CONTAINER inside isReservedSupported function, run on sailfish.
It shows that Build.IS_CONTAINER=false and the test still passes (i.e.,
isReservedSupported is correctly true).
Also checked that Build.IS_CONTAINER in isReservedSupported is true in
ARC++.
Bug: 111287848

Change-Id: I9af1f6cce5bab75ef941989bf279cf40c52e62b0