sepolicy: Allow system app to set boot anim property

Addresses denials observerd when using QuickBoot:

<4>[  224.756971] avc:  denied  { set } for property=ctl.bootanim scontext=u:r:system_app:s0 tcontext=u:object_r:ctl_bootanim_prop:s0 tclass=property_service
<3>[  224.757094] init: sys_prop: Unable to start service ctl [bootanim] uid:1000 gid:1000 pid:6039
<4>[  226.306456] avc:  denied  { set } for property=ctl.bootanim scontext=u:r:system_app:s0 tcontext=u:object_r:ctl_bootanim_prop:s0 tclass=property_service

Change-Id: I338a0a1d5fa12c10e413769ea9638c10ed137000