Pass DESTDIR down to python Makefile

In order to get a cleaner build out of the rpms we should
pass down the DESTDIR to the python Makefiles.  Then we
can use them instead of hard coding other inteligence into
the spec files.

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

Closes: #1214
Approved by: baude

contrib/python/pypodman/Makefile

@@ -1,4 +1,5 @@
 PYTHON ?= /usr/bin/python3
+DESTDIR := /
 
 .PHONY: python-pypodman
 python-pypodman:
@@ -14,7 +15,7 @@ integration:
 
 .PHONY: install
 install:
-	$(PYTHON) setup.py install
+	$(PYTHON) setup.py install --root ${DESTDIR}
 
 .PHONY: clobber
 clobber: uninstall clean