Do not fail on storage nodes if rsync of rings fails

This can mean that the ring-compute node is not accessible, that its
rsync service is not enabled or that the ring files are missing.

These errors can only happen if there's an error while applying the
ring-compute role on the ring-compute node, which means that the
proposal will fail to apply anyhow.

However, since the storage role is applied twice, including just before
the ring-compute role, if the ring-compute role fails to apply, then we
will hit this error and we will not be able to get the ring-compute role
re-applied. And therefore we will be stuck here.

For the same reason, we now only start the services if the relevant ring
file is present.

Part of https://bugzilla.novell.com/show_bug.cgi?id=861089
Merge pull request #195 from vuntz/missing-ring

Do not fail on storage nodes if rsync of rings fails
create ssl certificate automatically for smoketest
install via zypper on SUSE based systems
Merge pull request #199 from jdsn/zypper-fix

install via zypper on SUSE based systems
Fail if storage node has no disk for swift

Currently, we do not say anything and people think the storage node will
do something while it's not true.
Merge pull request #201 from jdsn/create-certificate

create ssl certificate automatically for smoketest
Merge pull request #207 from vuntz/fail-if-no-disk

Fail if storage node has no disk for swift
Merge pull request #191 from vuntz/havana-templates

Sync templates with Havana
Fix keystone-signing directory
Merge pull request #209 from vuntz/signing_dir

[roxy] Fix keystone-signing directory
Moved role constraints into model and removed edit deployment

(cherry picked from commit aa6290199261400be0f71dd5d638f384fb467f02)
Merge pull request #217 from vuntz/release/roxy/master

Moved role constraints into model and removed edit deployment
Removed the single assignment block from constraints
Merge pull request #218 from tboerger/feature/roxy/fix-constraints

Removed the single assignment block from constraints
Fix to work when keystone is behind haproxy
Use new helpers to get hostnames for endpoints
Generate dispersion.conf before running swift-dispersion-populate
HAProxy support for swift-proxy
Stop hardcoding 8080 port in several places

Using default attributes is just safer.