introduce pip_install_gr

This creates a new pip_install_gr that installs from global
requirements allowed versions. Now that stable branches are getting
capped all of devstack needs to be fixed to do things like this.

Change-Id: I8fd0ef2bfc544ca2576fab09d3018f760b8848fe
diff --git a/lib/zaqar b/lib/zaqar
index 34f1915..8d51910 100644
--- a/lib/zaqar
+++ b/lib/zaqar
@@ -140,10 +140,10 @@
 function configure_redis {
     if is_ubuntu; then
         install_package redis-server
-        pip_install redis
+        pip_install_gr redis
     elif is_fedora; then
         install_package redis
-        pip_install redis
+        pip_install_gr redis
     else
         exit_distro_not_supported "redis installation"
     fi