Changes

asterisk: pjsip.conf: Mark templates accordingly

Mark templates as such, in order to remove error messages during
asterisk setup when trying to apply the templates (which lack fields
such as "username", provided by config sections using the templates).

Reference: https://docs.asterisk.org/Fundamentals/Asterisk-Configuration/Asterisk-Configuration-Files/Templates/Template-Syntax/

Change-Id: Ia132c2e90cf6ee44145ca2e2555cf2dc6c1cfd51