Set the Chapel environment in clients when parallel testing

[reviewed by Tom]

This commit enables parallel testing using any setting of the Chapel
environment variables.  Prior to this only CHPL_COMM was handled (via
the -comm flag).

I did this by using the results of '$CHPL_HOME/util/printchplenv --sh'
in paratest.server and passing that along to paratest.client.  Since
the shell invoked from the system() call interprets the '' in the
results, I removed them before passing settings to the client.  If we
ever start having Chapel env var setting with spaces in them, we'll
have to handle that situation (probably best done by *not* using the
system command).

I also removed the -comm flag from paratest.* and start_test and
updated some comments where I was in there.




git-svn-id: http://svn.code.sf.net/p/chapel/code/trunk@21882 3a8e244f-b0f2-452b-bcba-4c88e055c3ca