Cap installed pip to be < 8

Pip 8 just release which made uninstalling distutils installed packages
fatal. This was previously a deprecation warning and is now causing all
dsvm jobs to fail.

Depends-On: I511d216d9d8619c7cf919c482aaead4e833cdaac
Change-Id: I22f5c3af1adf96cfbd5747122f915a82e947843a
diff --git a/tools/cap-pip.txt b/tools/cap-pip.txt
new file mode 100644
index 0000000..1a6f80c
--- /dev/null
+++ b/tools/cap-pip.txt
@@ -0,0 +1 @@
+pip<8