Change permissions of /data/misc/virtualizationservice

The folder is used for temporary files of virtualizationservice, with
a subfolder for each running VM. This wil continue to be the case but
each subfolder will be populated by a different instance of virtmgr,
running under the UID of the client (as opposed to system UID of
virtualizationservice).

To this end, change the permission mask of the root folder from 0770 to
0775. This gives non-system UIDs the permission to search the root
folder. This is necessary for the clients to be able to search their
own subfolder. It does not give them permission to read other
subfolders as those will be owned by different client UIDs.

Bug: 245727626
Test: atest -p packages/modules/Virtualization:avf-presubmit
Change-Id: Ie6e3be601ccb3b385f70bcf5b31bf8fff3aff8bc