cellular: Handle slow modem resume in network_MobileSuspendResume

BUG=chromium:233411
TEST=network_MobileSuspendResume

Change-Id: I6a803aee9395d4c26b818ccfba6658815fa0a49c
Reviewed-on: https://gerrit.chromium.org/gerrit/48664
Reviewed-by: Arman Uguray <armansito@chromium.org>
Commit-Queue: Thieu Le <thieule@chromium.org>
Tested-by: Thieu Le <thieule@chromium.org>
diff --git a/client/site_tests/network_MobileSuspendResume/network_MobileSuspendResume.py b/client/site_tests/network_MobileSuspendResume/network_MobileSuspendResume.py
index 3f91343..bd09864 100644
--- a/client/site_tests/network_MobileSuspendResume/network_MobileSuspendResume.py
+++ b/client/site_tests/network_MobileSuspendResume/network_MobileSuspendResume.py
@@ -108,15 +108,15 @@
     # There appears to be an issue after suspend/resume where GetProperties
     # returns with UnknownMethod called until some time later.
     def __get_mobile_device(self, timeout=TIMEOUT):
-        start_time = time.time()
-        device = self.FindMobileDevice(timeout)
-
         properties = None
+        start_time = time.time()
         timeout = start_time + timeout
         while properties is None and time.time() < timeout:
             try:
+                device = self.FindMobileDevice(timeout)
                 properties = device.GetProperties(utf8_strings=True)
-            except:
+            except dbus.exceptions.DBusException:
+                logging.debug('Mobile device not ready yet')
                 properties = None
 
             time.sleep(1)