init.rc: mkdir /data/anr 0775 system system

Ensure that /data/anr always exists. This allows us to eliminate
some code in system_server and dumpstate. In addition, this change
solves a common problem where people would create the directory
manually but fail to set the SELinux label, which would cause
subsequent failures when they used the directory for ANRs.

Bug: 22385254
Change-Id: I29eb3deb21a0504aed07570fee3c2f87e41f53a0