Do not use pip 10 or higher

It looks pip 10 failed the uninstallation of distutils installed
packages. This patch temporarily cap the version of pip to work-around. 

Closes-Bug: #1763966
Change-Id: I8bf80efc04883cd754c19bea0303064080112c6e
diff --git a/tools/cap-pip.txt b/tools/cap-pip.txt
index c280267..f5278d7 100644
--- a/tools/cap-pip.txt
+++ b/tools/cap-pip.txt
@@ -1 +1 @@
-pip!=8
+pip!=8,<10