Add locale override for space identification

If role is runned for an AIO build and deployers machine has
non-EN locale, awk won't simply work which makes role fail
with "Not enough space available".

Change-Id: Iae2ec4e8b7ba5b00c287a029ec0f2415af525402

tests/roles/bootstrap-host/tasks/check-requirements.yml

@@ -55,6 +55,8 @@
     else
         df -BK / | awk '!/^Filesystem/ {print $4}' | sed 's/K//'
     fi
+  environment:
+    LC_ALL: en_US.UTF-8
   when:
     - bootstrap_host_data_disk_device == None
   changed_when: false