test: Add test to verify helpers used for backing file name parsing

Add two test cases to verify that the helpers split and parse the
backing store components properly.

(cherry picked from commit 95a56835)

tests/virstringtest.c

@@ -567,6 +567,9 @@ mymain(void)
     const char *tokens7[] = { "The", "quick", "brown", "fox", "", NULL };
     TEST_SPLIT("The quick brown fox ", " ", 0, tokens7);
 
+    const char *tokens8[] = { "gluster", "rdma", NULL };
+    TEST_SPLIT("gluster+rdma", "+", 2, tokens8);
+
     if (virtTestRun("strdup", testStrdup, NULL) < 0)
         ret = -1;
 

tests/viruritest.c

@@ -173,6 +173,7 @@ mymain(void)
     TEST_PARSE("test://127.0.0.1:123/system", "test", "127.0.0.1", 123, "/system", NULL, NULL, NULL, NULL);
     TEST_PARSE("test://[::1]:123/system", "test", "::1", 123, "/system", NULL, NULL, NULL, NULL);
     TEST_PARSE("test://[2001:41c8:1:4fd4::2]:123/system", "test", "2001:41c8:1:4fd4::2", 123, "/system", NULL, NULL, NULL, NULL);
+    TEST_PARSE("gluster+rdma://example.com:1234/gv0/vol.img", "gluster+rdma", "example.com", 1234, "/gv0/vol.img", NULL, NULL, NULL, NULL);
 
     virURIParam params1[] = {
         { (char*)"foo", (char*)"one", false },