Allow dash in name of junit_tests rule

So far, if the name of the rule contained a dash (hyphen), as in
high-availability plugin for example, the test execution failed with
error message:

 bazel-out/local-fastbuild/bin/high-availability_testsTestSuite.java:6:
 error: '{' expected
 public class high-availability_testsTestSuite {}
                  ^
This is due to the fact that dashes are not valid characters in the name
of a Java class.

Workaround this by replacing any dash with an underscore.

Change-Id: I80fd4c5bcff0d2af6f337636bd942f30d6a521c6
diff --git a/tools/junit.bzl b/tools/junit.bzl
index 19974a7..c820d10 100644
--- a/tools/junit.bzl
+++ b/tools/junit.bzl
@@ -63,7 +63,7 @@
 )
 
 def junit_tests(name, srcs, **kwargs):
-    s_name = name + "TestSuite"
+    s_name = name.replace("-", "_") + "TestSuite"
     _GenSuite(name = s_name,
               srcs = srcs,
               outname = s_name)