autotest: Delete an SSH roundtrip in CrosHost.reboot()

This would often timeout and fail because reboot() is used in response
to the DUT not being available over SSH.

BUG=chromium:881209
TEST=python
> import common
> from autotest_lib.server import hosts
> from server import site_utils as server_utils
> from autotest_lib.server.hosts import host_info
> h = hosts.create_host(machine={
          'hostname': 'SOME_HOSTNAME',
          'afe_host': server_utils.EmptyAFEHost(),
          'host_info_store': host_info.InMemoryHostInfoStore(
              host_info.HostInfo(label=['board:link'])),
  })
> h.reboot()

Change-Id: Ic7411c348dd93fbb76bf87198a061ce643c82943
Reviewed-on: https://chromium-review.googlesource.com/1227377
Commit-Ready: Prathmesh Prabhu <pprabhu@chromium.org>
Tested-by: Prathmesh Prabhu <pprabhu@chromium.org>
Reviewed-by: Allen Li <ayatane@chromium.org>
diff --git a/server/hosts/cros_host.py b/server/hosts/cros_host.py
index f7a248f..755fe70 100644
--- a/server/hosts/cros_host.py
+++ b/server/hosts/cros_host.py
@@ -1034,19 +1034,15 @@
         if 'fastsync' not in dargs:
             dargs['fastsync'] = True
 
-        # For purposes of logging reboot times:
-        # Get the board name i.e. 'daisy_spring'
-        board_fullname = self.get_board()
-
-        # Strip the prefix and add it to dargs.
-        dargs['board'] = board_fullname[board_fullname.find(':')+1:]
+        dargs['board'] = self.host_info_store.get().board
         # Record who called us
         orig = sys._getframe(1).f_code
         metric_fields = {'board' : dargs['board'],
                          'dut_host_name' : self.hostname,
                          'success' : True}
         metric_debug_fields = {'board' : dargs['board'],
-                               'caller' : "%s:%s" % (orig.co_filename, orig.co_name),
+                               'caller' : "%s:%s" % (orig.co_filename,
+                                                     orig.co_name),
                                'success' : True,
                                'error' : ''}