fix AVC denial fordocker run --init

[bcressey]

Issue number:
Closes #1082

Description of changes:
docker-init has the runtime_exec_t label, rather than one of the labels that signify local content, but it's still a valid entrypoint to the container domains.

Testing done:

# docker run -it --init --rm debian
...
root@6644230d2e95:/# ls -l /proc/1/exe
lrwxrwxrwx. 1 root root 0 Aug 27 17:32 /proc/1/exe -> /sbin/docker-init

root@6644230d2e95:/# ls -lZ /sbin/docker-init
-rwxr-xr-x. 1 root root system_u:object_r:runtime_exec_t:s0 589280 Aug 24 17:23 /sbin/docker-init

Terms of contribution:

By submitting this pull request, I agree that this contribution is dual-licensed under the terms of both the Apache License, version 2.0, and the MIT license.

[webern]

🤓