Fix "Revision:" line in nightly emails.

Using mysystem let the actual version go to stdout and the exit status was
included in the email. Now the version is correctly piped and included in the
email.

git-svn-id: http://svn.code.sf.net/p/chapel/code/trunk@23768 3a8e244f-b0f2-452b-bcba-4c88e055c3ca