This patch rehomes a bulk of neutron.plugins.common.utils into
neutron-lib. What's left in the neutron plugin utils will be made
private upon consumption.
In addition this patch also enhances the is_valid_* functions of
the utils to ensure the range value is a number. The previous
implementation allowed passing boolean values for tunnel ranges.
UTs and a release note are also included.
For a sample consumption patch see
Ifcb39c08706d7a12f3ebd5865eb6d2edb95eed45
Change-Id: Iabb155b5d2d0ec6104ebee5dd42cf292bdf3ec61
3dfa6229d1