Fix version parsing for cistem package (#9260)

Adds 'code' to the list of suffixes that are excluded from version
parsing of URLs, such that if a URL contains the string
'cistem-1.0.0-beta-source-code', a version X will substitute in to
produce a URL with cistem-X-source-code ('source' was already excluded).
The 'cistem' package version is updated to make use of this (and fix
a fetching bug with the cistem package). A unit test is added to check
this parsing case.

lib/spack/spack/test/url_parse.py

@@ -43,6 +43,8 @@
     ('jpegsrc.v9b', 'jpegsrc.v9b'),
     ('turbolinux702', 'turbolinux702'),
     ('converge_install_2.3.16', 'converge_install_2.3.16'),
+    # Download type - code, source
+    ('cistem-1.0.0-beta-source-code', 'cistem-1.0.0-beta'),
     # Download type - src
     ('apache-ant-1.9.7-src', 'apache-ant-1.9.7'),
     ('go1.7.4.src', 'go1.7.4'),

lib/spack/spack/url.py

@@ -169,6 +169,7 @@ def strip_version_suffixes(path):
         # Download type
         '[Ii]nstall',
         'all',
+        'code',
         'src(_0)?',
         '[Ss]ources?',
         'file',