nethvoice: set unified timezone value across all components

[Stell0]

PRs:

• https://github.com/nethesis/ns8-nethvoice/pull/143
• https://github.com/nethesis/nethvoice-cti/pull/203
• https://github.com/nethesis/nethvoice-cti/pull/204
• https://github.com/nethesis/ns8-nethvoice/pull/147
• https://github.com/nethesis/ns8-nethvoice/pull/149

[Amygos]

Waiting for release 0.0.8 of https://github.com/nethesis/nethvoice-cti to close this issue.