Fix riak container nested docker mounts

Fix docker mounts to allow the riak docker container
to be started nested.
Also note about nested containers in the docs.

Related-bug: #1548851
Related-bug: #1547587

Change-Id: I2fb448ac439b717eae1c3deee2cd067ac8b4f0c7
Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>

bootstrap/playbooks/riak.yaml

@@ -1,9 +1,11 @@
+- file: path=/var/tmp/vagrant state=directory
+- copy: src=/vagrant/utils/riak/app.config dest=/var/tmp/vagrant/riak-app.config
 - name: start riak container
   docker:
     name: vagrant_riak_1
     image: solarproject/riak
     volumes:
-        - /vagrant/utils/riak/app.config:/etc/riak/app.config
+      - /var/tmp/vagrant/riak-app.config:/etc/riak/app.config
     ports:
       - 8087:8087
       - 8098:8098

doc/source/faq.rst

@@ -36,7 +36,7 @@ Just update resource::
 How can I run solar worker ?
 -----------------------------------
 
-- If you use `vagrant` then you can just `sudo start solar-worker` 
+- If you use `vagrant` then you can just `sudo start solar-worker`
   as `vagrant` user.
 
 How can I configure solar ?
@@ -45,10 +45,10 @@ How can I configure solar ?
 There are several places where we search for config values:
 
 1. `.config` file in CWD or in path from `SOLAR_CONFIG` env variable
-2. if env `SOLAR_CONFIG_OVERRIDE` contains valid path then it override 
+2. if env `SOLAR_CONFIG_OVERRIDE` contains valid path then it override
    previous values
 3. `.config.override` in CWD
-4. You can also set upper-cased env variable which matches one of those in 
+4. You can also set upper-cased env variable which matches one of those in
    config
 
 .. _faq_what_database: