Prune archive journal log

There is a case seen on system where the journal had filled up
the /run/ filesystem. Apparently we don’t prune that yet in code
for cleanup.

Command Example : "journalctl —vacuum-size=1M"
Defaulted to 1 Meg in the utils.robot.

Resolves openbmc/openbmc-test-automation#231

Change-Id: I93fa162a77b24ce06926ee3ddf485520a90e5e11
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
diff --git a/lib/utils.robot b/lib/utils.robot
index 7cb0ad7..6c8099c 100755
--- a/lib/utils.robot
+++ b/lib/utils.robot
@@ -501,3 +501,21 @@
     ...    return_stderr=True  return_rc=True
     Should Be True    ${count}==0
     Should Be Empty    ${stderr}
+
+Prune Journal Log
+    [Documentation]   Prune archived journal logs.
+    [Arguments]   ${vacuum_size}=1M
+
+    # This keyword can be used to prevent the journal
+    # log from filling up the /run filesystem.
+    # This command will retain only the latest logs
+    # of the user specified size.
+
+    Open Connection And Log In
+    ${output}  ${stderr}  ${rc}=
+    ...  Execute Command
+    ...  journalctl --vacuum-size=${vacuum_size}
+    ...  return_stderr=True  return_rc=True
+
+    Should Be Equal  ${rc}  ${0}  msg=${stderr}
+    Should Contain   ${stderr}  Vacuuming done