ANDROID: incremental fs: Evict inodes before freeing mount data

Since evicting inodes triggers writes to the backing file, which uses
the mi_owner field from the mount_info struct, make sure inodes are
evicted before we free the mount_info data

Test: incfs_test
Bug: 270117845
Change-Id: I673b2e0e04b5adc3998caf6f22443598a30338af
Signed-off-by: Paul Lawrence <paullawrence@google.com>