Remove SELinux context manipulations during injection (#87)

After few tests in various devices, it seems that SELinux context modifications are unnecessary for the injection to work.

We thus remove all related manipulations. Further (partial) reverting of the commit must be justified with SELinux logs:

> adb shell su -c 'cat /proc/kmsg | grep avc'

module/sepolicy.rule

@@ -1,5 +1,2 @@
-allow keystore system_file unix_dgram_socket *
-allow system_file keystore unix_dgram_socket *
-allow keystore system_file file *
 allow keystore shell_data_file dir *
 allow crash_dump keystore process *