opt in for neutron-lib consumption patches

As part of the Denver PTG [1] we decided networking related projects
that are "current" and want to receive neutron-lib consumption patches
on an on-going basis should indicate such with a well defined comment
in their requirements.txt. This allows us to easily find the list of
project to receive neutron-lib consumption patches [2] by searching for
the string.

In addition, projects opting-in for these patches are also attesting
they will stay up to date with TC and infra initiatives to ensure
consumption patches can flow freely.

This patch adds the "neutron-lib-current" string to requirements.txt
opting in for neutron-lib consumption patches.

[1] https://etherpad.openstack.org/p/neutron-stein-ptg
[2] https://docs.openstack.org/neutron-lib/latest/contributor/contributing.html#phase-4-consume

Change-Id: I7a2e538ad345d4a2d1cb398c3c325916f54df9e1

requirements.txt

@@ -16,3 +16,9 @@ oslo.config>=5.1.0 # Apache-2.0
 pypowervm>=1.1.11 # Apache-2.0
 setuptools!=24.0.0,!=34.0.0,!=34.0.1,!=34.0.2,!=34.0.3,!=34.1.0,!=34.1.1,!=34.2.0,!=34.3.0,!=34.3.1,!=34.3.2,!=36.2.0,>=21.0.0 # PSF/ZPL
 neutron-lib>=1.18.0 # Apache-2.0
+
+# The comment below indicates this project repo is current with neutron-lib
+# and should receive neutron-lib consumption patches as they are released
+# in neutron-lib. It also implies the project will stay current with TC
+# and infra initiatives ensuring consumption patches can land.
+# neutron-lib-current