bearer-mbim: increase timeout for deactivating IP session to 60s

Since commit 0c7f3380a ("bearer-mbim: ensure session is disconnected
before trying to connect"), MMBearerMbim always issues a
MBIM_CID_CONNECT (MBIMActivationCommandDeactivate) command before a
MBIM_CID_CONNECT (MBIMActivationCommandActivate) command during a
connection attempt. That is to ensure that an IP session is actually
deactivated before we try to activate a new IP session.

Unfortunately, it's been observed on Huawei ME936 that it takes more
than 30s for the modem to respond to a MBIM_CID_CONNECT
(MBIMActivationCommandDeactivate) command when trying to deactivate a
session that hasn't been activated.

When the signal is weak, it's also possible that a modem takes more than
30s to deactivate an IP session during a disconnection attempt.

This patch increases the timeout for deactivating an IP session from 30s
to 60s in both connection and disconnection attempt.

src/mm-bearer-mbim.c

@@ -851,7 +851,7 @@ connect_context_step (GTask *task)
 
         mbim_device_command (ctx->device,
                              message,
-                             30,
+                             60,
                              NULL,
                              (GAsyncReadyCallback)ensure_disconnected_ready,
                              task);
@@ -1254,7 +1254,7 @@ disconnect_context_step (GTask *task)
 
         mbim_device_command (ctx->device,
                              message,
-                             30,
+                             60,
                              NULL,
                              (GAsyncReadyCallback)disconnect_set_ready,
                              task);