Please backport bubblewrap 0.1.7-1 (universe) from zesty

[Clint Byrum]

Please backport bubblewrap 0.1.7-1 (universe) from zesty to xenial

Reason for the backport:
========================
This is a highly useful package for sandboxing applications quickly with minimal overhead. While Xenial's default kernel does not support all of the USER_NS features, the Yakkety and later backports do.

Testing:
========
* xenial:
[X] Package builds without modification
[ ] bubblewrap-dbgsym installs cleanly and runs -- I built locally and did not produce dbgsym's
[X] bubblewrap installs cleanly and runs

Reverse dependencies:
=====================
The package was already updated to 0.1.7 in a yakkety SRU, and there are no reverse dependencies in Xenial.