Add IPMI timeout option "-N" to the command execution

Changes:
    - By default 3 seconds timeout
    - User can override the timeout by using CLI option
      "-v IPMI_TIMEOUT:<value>"

Resolves  openbmc/openbmc-test-automation#2111

Change-Id: I7cabd060f3652e4f9ebf98029e204c53f89ed14f
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
diff --git a/lib/resource.robot b/lib/resource.robot
index 401cbe9..4d8ba43 100755
--- a/lib/resource.robot
+++ b/lib/resource.robot
@@ -44,6 +44,8 @@
 ${IPMI_COMMAND}    External
 # IPMI chipher default.
 ${IPMI_CIPHER_LEVEL}  ${17}
+# IPMI timeout default.
+${IPMI_TIMEOUT}       ${3}
 
 # PDU related parameters
 ${PDU_TYPE}         ${EMPTY}