Fix for bugs 1359361 1360444 1359366 1360449

Bug 1359361: Scripts that required --nodes (trafodion_setup,
ambari_uninstall, cloudera_uninstall, mapr_uninstall) will now return an error
if a node list has not be given.

Bug 1360444: pdsh commands are now only after pdsh has been installed.

Bug 1359366: An error message to fix http_proxy settings is in
trafodion_setup if can not download.

Bug 1360449: Checking for existance of /etc/selinux/config before
copying file.

Change-Id: I2dedc18ac1825b80055fcb2b2e2edb28a7e53001