Fix bug 2412: fix identification of bootable volume

The volume identification done during the test Basic28 to identify
the root volume and the ordinary volume fails, leading to a sequence of
failed test cases.

After upgrading pip dependencies or after recent changes in the VIM, the
command line used to get a volume and check if it is bootable is
returning "True", while the if clause is comparing its value with "true".

openstack volume show ${volume_id} | grep bootable | awk '{print $4}'

This commit fixes it by converting the obtained value to lower case before
the comparison.

Change-Id: Ie6c8d11fb27fbd0fe10e256bc6688a7cd5cb5388
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>
diff --git a/robot-systest/lib/openstack_lib.resource b/robot-systest/lib/openstack_lib.resource
index b1c0875..64be1b4 100644
--- a/robot-systest/lib/openstack_lib.resource
+++ b/robot-systest/lib/openstack_lib.resource
@@ -99,6 +99,7 @@
     [Arguments]   ${volume_match}   ${index}
     Should Not Be Empty   ${volume_match}   ${index}
     ${bootable}=   Check If Volume Bootable   ${volume_match}[${index}]
+    ${bootable}=   Convert To Lowercase   ${bootable}
     IF   '${bootable}'=='true'
         Set Suite Variable   ${ROOT_VOL_ID}   ${volume_match}[${index}]
         IF   not ${index}