tests/azure: Deactivate NTP in prepare-build

In CentOS 8 and also Fedora the configuration and start of chrony
fails with

  Fatal error : adjtimex(0x8001) failed : Operation not permitted

For more information: https://bugzilla.redhat.com/show_bug.cgi?id=1772053

NTP will not be needed before a separate namespace is used for clocks.