[install] Fix install_rally.sh

install_rally.sh fails to find bindep.txt if the script
is downloaded separately.

This patch moves logic related to bindep to the place where
rally repo already cloned.

Closes-Bug: #1652917
Change-Id: Ia43b25461696f681a2e3b13a13636b95aabafae7

bindep.txt

@@ -3,7 +3,6 @@
 
 build-essential [platform:dpkg]
 gcc [platform:rpm]
-git
 gmp-devel [platform:rpm]
 libffi-dev [platform:dpkg]
 libffi-devel [platform:rpm !platform:opensuse]
@@ -20,4 +19,3 @@ postgresql93-devel [platform:opensuse]
 python-dev [platform:dpkg]
 python-devel [platform:rpm]
 redhat-rpm-config [platform:rpm]
-wget