verify-kernel-boot-log.sh: don't SKIP when i915 is missing

`grep something missing_file` returns 2. When the file is missing this
is misinterpreted as SKIP as seen in daily test run 20752. This happens
because the grep is the last command in the subshell.

The `grep /sys/kernel/debug/dri/0/i915_display_info` and the including
subshell are not part of the test; ignore their exit code and let the rest
of the test code decide what the exit value of the test is.

Fixes commit aadd770

Signed-off-by: Marc Herbert <marc.herbert@intel.com>

Author: marc-hb

test-case/verify-kernel-boot-log.sh

@@ -66,6 +66,7 @@ wait_is_system_running()
         DISPLAY=:0 xrandr --listmonitors
         DISPLAY=:1024 xrandr --listmonitors
         sudo grep -i connected /sys/kernel/debug/dri/0/i915_display_info
+        true
     )
     die "Some services are not running correctly"
 }