Create the .nomedia file in paths that are not scannable

This is useful when user ejects the SD card and brings it to an older
device and its media scanner can now correctly identify these paths as
not scannable.

Test: atest ExternalStorageHostTest#testVerifyNoMediaCreated
Bug: 156137949, 156273422
Change-Id: Idd8dcf5e875bd4a580244358065ad0acf168bd10
1 file changed