Install ceilometer from pypi

Since ceilometer is introduced in upper-constraints.txt [1], tests are
failing, as ceilometer was installed via tox.ini directly from github,
but pip doesn't like that:

"Could not satisfy constraints for 'ceilometer': installation from path
 or url cannot be constrained to a version"

[1] https://review.openstack.org/#/c/601498

Change-Id: I9a018f625e6f252fe64ee2b8b93f5f2e0b464309

lower-constraints.txt

@@ -4,6 +4,7 @@ automaton==1.9.0
 Babel==2.3.4
 bashate==0.5.1
 cachetools==2.0.0
+ceilometer==11.0.0
 contextlib2==0.4.0
 coverage==4.0
 debtcollector==1.2.0

requirements.txt

@@ -5,3 +5,4 @@ oslo.log>=3.36.0 # Apache-2.0
 pbr!=2.1.0,>=2.0.0 # 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
+ceilometer>=11.0.0

tox.ini

@@ -23,7 +23,6 @@ deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt}
   -r{toxinidir}/requirements.txt
   -r{toxinidir}/test-requirements.txt
-  -egit+https://git.openstack.org/openstack/ceilometer#egg=ceilometer
   -rhttps://git.openstack.org/cgit/openstack/ceilometer/plain/test-requirements.txt
 whitelist_externals =
   bash
@@ -90,5 +89,4 @@ deps =
   -c{toxinidir}/lower-constraints.txt
   -r{toxinidir}/test-requirements.txt
   -r{toxinidir}/requirements.txt
-  -egit+https://git.openstack.org/openstack/ceilometer#egg=ceilometer
   -rhttps://git.openstack.org/cgit/openstack/ceilometer/plain/test-requirements.txt