Re-factor hadoop classes for multiple distros

Standardize slave node naming to include distro. Grand-father in
the existing slaveNN node names.

Fold cloudera_slave and horton_slave classes back into slave
by adding a "distro" parameter.
Now supports: HDP1.3, HDP2.1, CDH4.4

Folding cloudera.pp and horton.pp into a single hadoop module
may be desirable in future.

Change-Id: Icd3c1734d770c8efebbd88064ddf71cf814426a9