Prevent adding transitions to kernel or init domains.

Add neverallow rules to prohibit adding any transitions into
the kernel or init domains.  Rewrite the domain self:process
rule to use a positive permission list and omit the transition
and dyntransition permissions from this list as well as other
permissions only checked when changing contexts.  This should be
a no-op since these permissions are only checked when
changing contexts but avoids needing to exclude kernel or init
from the neverallow rules.

Change-Id: Id114b1085cec4b51684c7bd86bd2eaad8df3d6f8
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>