Handle policy reloads within installd rather than restarting it.

Restarting installd upon policy reloads has reportedly caused
stability problems for some users.  Stop restarting installd
and instead handle policy reloads within it.

Change-Id: I697a736d8e414cfc6cfa131ed7b97c7f7694d022
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>