Added tests for power button in overview page

Changes:
    - Test is verifying server power button in Overview page
    - Added xpath_server_power_header xpath

Change-Id: I95418824456a6ecbb0df3217edc4bf94c371aa0d
Signed-off-by: Sushma M M <sushmm99@in.ibm.com>
diff --git a/gui/data/resource_variables.py b/gui/data/resource_variables.py
index 994749b..e1e282b 100644
--- a/gui/data/resource_variables.py
+++ b/gui/data/resource_variables.py
@@ -133,6 +133,7 @@
     xpath_profile_settings = "//a[@href='#/profile-settings']"
     xpath_server_health_header = "//*[@data-test-id='appHeader-container-health']"
     xpath_event_header = "//h1[text()="Event logs"]"
+    xpath_server_power_header = "//*[@data-test-id='appHeader-container-power']"
 
     # xpath for health menu
     xpath_health_menu = "//button[@aria-controls='health-menu']"