Regex validation for aliases in swift_storage_policy provider does not
allow single alias value, like for exemple:
swift::storage::policy { '1':
policy_name => '3-Replica-Policy',
policy_aliases => 'green',
This fixes the accepted pattenr to allow single-value for policy_aliases
parameter.
Also, the whole expression is updated to more strictly validate
the pattern, especially when more than 2 aliases are given.
Change-Id: I62c86097c717d2a74c100386cf20e07976571805