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/ironic b/lib/ironic
index c8481ab..7afed05 100644
--- a/lib/ironic
+++ b/lib/ironic
@@ -206,7 +206,7 @@
         sudo install -D -m 0644 -o $STACK_USER {${GITDIR["python-ironicclient"]}/tools/,/etc/bash_completion.d/}ironic.bash_completion
     else
         # nothing actually "requires" ironicclient, so force instally from pypi
-        pip_install python-ironicclient
+        pip_install_gr python-ironicclient
     fi
 }
 
@@ -729,7 +729,7 @@
 
     # install diskimage-builder
     if [[ $(type -P ramdisk-image-create) == "" ]]; then
-        pip_install diskimage_builder
+        pip_install_gr "diskimage-builder"
     fi
 
     if [ -z "$IRONIC_DEPLOY_KERNEL" -o -z "$IRONIC_DEPLOY_RAMDISK" ]; then