Add parameter to override locale to utils.execute

In common.utils.mkfs and in common.disk_partitioner.list_partitions
functions standard locale is required in order to get correct console
output. In this change use_standard_locale flag is added to
common.utils.execute function to avoid code duplication when copying
environment variables and setting correct loacale.

Change-Id: Icd0ceb7b588d435eba9eb30846a9c66565e98a5e
Merge "Add parameter to override locale to utils.execute"