parsoid: role class for beta and factor out common code

This patch introduce the new role::parsoid::beta, I factored out common
code in the new role::parsoid::common leaving the specific bits in the
production and beta classes.

The main difference is the symbolic link for the Parsoid extension. In
production that is using the nameless deployment system while on beta it
is on the shared NFS export.

bug: 57233
Change-Id: Ia9f2f0466fb5d4a77684dfaa8ed3d4fa31658b15
Merge "parsoid: role class for beta and factor out common code" into production