Fix os-distro property name to os_distro

For fedora-atomic image, we set a property named os_distro.
However, in error logs and documentation refer to it as os-distro

Closes-Bug: #1470934
Change-Id: Ifc5a5be8e0131743aba88a143098d05e5cbac951

doc/source/dev/dev-manual-devstack.rst

@@ -98,7 +98,7 @@ Create a new shell, and source the devstack openrc script::
     glance image-create --name fedora-21-atomic-3 \
                         --is-public True \
                         --disk-format qcow2 \
-                        --property os-distro='fedora-atomic'\
+                        --property os_distro='fedora-atomic'\
                         --container-format bare < fedora-21-atomic-3.qcow2
     test -f ~/.ssh/id_rsa.pub || ssh-keygen
     nova keypair-add --pub-key ~/.ssh/id_rsa.pub testkey

magnum/common/exception.py

@@ -464,7 +464,7 @@ class ImageNotAuthorized(MagnumException):
 
 
 class OSDistroFieldNotFound(ResourceNotFound):
-    message = _("Image %(image_id)s doesn't contain os-distro field.")
+    message = _("Image %(image_id)s doesn't contain os_distro field.")
 
 
 class KubernetesAPIFailed(MagnumException):

magnum/locale/magnum.pot

@@ -328,7 +328,7 @@ msgstr ""
 
 #: magnum/common/exception.py:460
 #, python-format
-msgid "Image %(image_id)s doesn't contain os-distro field."
+msgid "Image %(image_id)s doesn't contain os_distro field."
 msgstr ""
 
 #: magnum/common/k8s_manifest.py:40 magnum/common/k8s_manifest.py:53