Add dev libs for xml2 and xslt to install_rally.sh
Add dev libs for xml2 and xslt to install_rally.sh

`libxml2-dev` and `libxslt1-dev` are missed from dependencies in
Rally installation script. This patch fixed this.

Change-Id: I1a2ea90a7b86df74f2357ca7fa4111973d4ef60e

eayunstack/rally,shdowofdeath/rally,gluke77/rally,openstack/rally,pandeyop/rally,gluke77/rally,gluke77/rally,vganapath/rally,eonpatapon/rally,eayunstack/rally,eonpatapon/rally,afaheem88/rally,aplanas/rally,openstack/rally,vefimova/rally,amit0701/rally,yeming233/rally,paboldin/rally,vponomaryov/rally,varunarya10/rally,afaheem88/rally,group-policy/rally,openstack/rally,paboldin/rally,amit0701/rally,go-bears/rally,paboldin/rally,redhat-openstack/rally,pyKun/rally,openstack/rally,yeming233/rally,group-policy/rally,pandeyop/rally,amit0701/rally,eayunstack/rally,vponomaryov/rally,vganapath/rally,shdowofdeath/rally,vganapath/rally,pyKun/rally,go-bears/rally,gluke77/rally,varunarya10/rally,vganapath/rally,cernops/rally,group-policy/rally,aplanas/rally,aforalee/RRally,cernops/rally,aforalee/RRally,redhat-openstack/rally,vefimova/rally