csmock: make kfp work for pkgs without the -release suffix

The code that extracts package name from the `name-version-release`
string did not work as expected if the `-release` part was missing.
Consequently, it did not find the corresponding `exclude-paths.txt`
file in the known-false-positives while scanning a source code tarball
named: `RedHatInsights-compliance-backend-bd2b8accb3d4aae88a8c1a71563ec3f5ead7b1fa.tar.gz`

Resolves: https://issues.redhat.com/browse/OSH-392
Closes: csutils#136

py/csmock

@@ -958,8 +958,11 @@ exceeds the specified limit (defaults to 1024).")
         else:
             props.nvr = re.sub("\\.tar$", "", re.sub("\\.[^.]*$", "", srpm_base))
 
-        # cut off version-release to obtain package name
-        props.pkg = re.sub("-[^-]+-[0-9][^-]*$", "", props.nvr)
+        # cut off the -version-release suffix to obtain package name (if -release is missing, cut -version only)
+        props.pkg = props.nvr
+        m = re.search(r"^(.*?)(-[^-]+)(-[0-9][^-]*)?$", props.nvr)
+        if m:
+            props.pkg = m.group(1)
 
     # resolve name of the file/dir we are going to store the results to
     if args.output is None: