Move keyring option to global section

Using vstart.sh -n uses ceph-authtool to generate the keyring file
in ./keyring.  The vstart.sh script then writes out the ceph.conf
with a keyring option in the [client] section, so when the monitors
start, they can't find a keyring file.  This commit puts the keyring in
the [global] section.

Signed-off-by: Sam Lang <sam.lang@inktank.com>

src/vstart.sh

@@ -272,9 +272,9 @@ EOF
         auth supported = cephx
 EOF
 			cat <<EOF >> $conf
+        keyring = $keyring_fn
 
 [client]
-        keyring = $keyring_fn
 
 [mds]
 $DAEMONOPTS