Advise users on using setsebool to set pulp_manage_rsync selinux boolean

F27+ changed the behavior of semanage to set a selinux boolean by
default, but not change its current state. Update docs to advise users
of this to avoid confusion when rsync distributors fail to run with
selinux in F27.

closes #3347
https://pulp.plan.io/issues/3347

docs/tech-reference/iso-rsync-distributor.rst

@@ -12,10 +12,15 @@ Configuration
 Pulp's SELinux policy includes a ``pulp_manage_rsync`` boolean. When enabled, the
 ``pulp_manage_rsync`` boolean allows Pulp to use rsync and make ssh connections. The boolean is
 disabled by default. The ISO Rsync distributor will fail to publish with SELinux Enforcing unless
-the boolean is enabled. To enable it, you can do this::
+the boolean is enabled. To enable it by default, you can do this::
 
     $ sudo semanage boolean --modify --on pulp_manage_rsync
 
+In F27+ `semanage` only sets the default state of an SELinux policy, an additional command must also
+be run to set its current state::
+
+    $ sudo setsebool pulp_manage_rsync on
+
 Here is an example iso_rsync_distributor configuration::
 
     {

docs/tech-reference/rsync-distributor.rst

@@ -12,10 +12,15 @@ Configuration
 Pulp's SELinux policy includes a ``pulp_manage_rsync`` boolean. When enabled, the
 ``pulp_manage_rsync`` boolean allows Pulp to use rsync and make ssh connections. The boolean is
 disabled by default. The RPM Rsync distributor will fail to publish with SELinux Enforcing unless
-the boolean is enabled. To enable it, you can do this::
+the boolean is enabled. To enable it by default, you can do this::
 
     $ sudo semanage boolean --modify --on pulp_manage_rsync
 
+In F27+ `semanage` only sets the default state of an SELinux policy, an additional command must also
+be run to set its current state::
+
+    $ sudo setsebool pulp_manage_rsync on
+
 Here's an example of rpm_rsync_distributor configuration::
 
     {