apparmor: ensure labels with more than one entry have correct flags

labels containing more than one entry need to accumulate flag info
from profiles that the label is constructed from. This is done
correctly for labels created by a merge but is not being done for
labels created by an update or directly created via a parse.

This technically is a bug fix, however the effect in current code is
to cause early unconfined bail out to not happen (ie. without the fix
it is slower) on labels that were created via update or a parse.

Signed-off-by: John Johansen <john.johansen@canonical.com>