Fix crash accessing a NULL URI when looking up auth credentials

When auto-probing hypervisor drivers, the conn->uri field will
initially be NULL. Care must be taken not to access members
when doing auth lookups in the config file
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

src/remote/remote_driver.c

@@ -3726,7 +3726,7 @@ static int remoteAuthFillFromConfig(virConnectPtr conn,
 
         if (virAuthConfigLookup(state->config,
                                 "libvirt",
-                                conn->uri->server,
+                                VIR_URI_SERVER(conn->uri),
                                 credname,
                                 &value) < 0)
             goto cleanup;

src/util/virauth.c

@@ -130,7 +130,7 @@ virAuthGetCredential(virConnectPtr conn,
 
     if (virAuthConfigLookup(config,
                             servicename,
-                            conn->uri->server,
+                            VIR_URI_SERVER(conn->uri),
                             credname,
                             &tmp) < 0)
         goto cleanup;

src/util/viruri.h

@@ -60,4 +60,6 @@ char *virURIFormatParams(virURIPtr uri);
 
 void virURIFree(virURIPtr uri);
 
+# define VIR_URI_SERVER(uri) ((uri) && (uri)->server ? (uri)->server : "localhost")
+
 #endif /* __VIR_URI_H__ */