Fix arc.is_android_process_running().

Android's ps command stopped accepting process name as an
argument since Android N:
https://android-review.googlesource.com/#/c/179678/

BUG=b:34864566
TEST=test_that samus cheets_SettingsBridge  # in M and N

Change-Id: I7c31d6297768b5b01da121b2807537f77f46ef5d
Reviewed-on: https://chromium-review.googlesource.com/435764
Commit-Ready: Shuhei Takahashi <nya@chromium.org>
Tested-by: Shuhei Takahashi <nya@chromium.org>
Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
diff --git a/client/common_lib/cros/arc.py b/client/common_lib/cros/arc.py
index 8c4a656..e2f9433 100644
--- a/client/common_lib/cros/arc.py
+++ b/client/common_lib/cros/arc.py
@@ -216,9 +216,8 @@
 
     @param process_name: Process name.
     """
-    output = adb_shell('ps %s' % pipes.quote(process_name))
-    # ps always prints the header.
-    return len(output.splitlines()) == 2
+    output = adb_shell('ps | grep %s' % pipes.quote(' %s$' % process_name))
+    return bool(output)
 
 
 def check_android_file_exists(filename):