Add flags for off-corp network testing.

For ssh port tunnelling of the servo_host ssh connection, allow setting
servo_host_port to a port other than 22.

For machines which can ssh, but not ping (such as off-corp Googler
workstations and CloudTop), allow disabling icmp with arg use_icmp=false

BUG=b:179033333
TEST=Ran firmware_ECWakeSource off the corp network against skylab DUT.

Change-Id: Ic6bca511f7b89cb0144690393d311889d7d2b497
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/autotest/+/2668598
Tested-by: Jeremy Bettis <jbettis@chromium.org>
Commit-Queue: Jeremy Bettis <jbettis@chromium.org>
Reviewed-by: Greg Edelston <gredelston@google.com>
diff --git a/server/hosts/servo_constants.py b/server/hosts/servo_constants.py
index e6463ca..0b39aaf 100644
--- a/server/hosts/servo_constants.py
+++ b/server/hosts/servo_constants.py
@@ -9,6 +9,7 @@
 # Names of the host attributes in the database that represent the values for
 # the servo_host and servo_port for a servo connected to the DUT.
 SERVO_HOST_ATTR = 'servo_host'
+SERVO_HOST_SSH_PORT_ATTR = 'servo_host_ssh_port'
 SERVO_PORT_ATTR = 'servo_port'
 SERVO_BOARD_ATTR = 'servo_board'
 # Model is inferred from host labels.
@@ -21,6 +22,7 @@
 SERVO_ATTR_KEYS = (
         SERVO_BOARD_ATTR,
         SERVO_HOST_ATTR,
+        SERVO_HOST_SSH_PORT_ATTR,
         SERVO_PORT_ATTR,
         SERVO_SERIAL_ATTR,
         SERVO_SETUP_ATTR,