Correct fix of the 'issue not found' error

After I9a0183b58 the its-jira plugin was not able to find
the issues because of an incorrect way of building the URL.
Remove the heading slash on the URL resources to prevent
the context root in the base url.

Bug: Issue 8263
Change-Id: I4f7da55dc68ef067ec06d2a869c31c060b762d91
diff --git a/src/main/java/com/googlesource/gerrit/plugins/its/jira/JiraClient.java b/src/main/java/com/googlesource/gerrit/plugins/its/jira/JiraClient.java
index 897d7aa..ae2a864 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/its/jira/JiraClient.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/its/jira/JiraClient.java
@@ -67,7 +67,7 @@
   public boolean issueExists(String issueKey) throws IOException {
     JiraRestApi<JiraIssue> api = apiBuilder.getIssue();
 
-    api.doGet("/" + issueKey, HTTP_OK, new int[] {HTTP_NOT_FOUND, HTTP_FORBIDDEN});
+    api.doGet(issueKey, HTTP_OK, new int[] {HTTP_NOT_FOUND, HTTP_FORBIDDEN});
     Integer code = api.getResponseCode();
     switch (code) {
       case HTTP_OK:
@@ -92,7 +92,7 @@
   public List<JiraTransition.Item> getTransitions(String issueKey) throws IOException {
 
     JiraRestApi<JiraTransition> api = apiBuilder.get(JiraTransition.class, "/issue");
-    return Arrays.asList(api.doGet("/" + issueKey + "/transitions", HTTP_OK).getTransitions());
+    return Arrays.asList(api.doGet(issueKey + "/transitions", HTTP_OK).getTransitions());
   }
 
   /**
@@ -106,7 +106,7 @@
       log.debug("Trying to add comment for issue {}", issueKey);
       apiBuilder
           .getIssue()
-          .doPost("/" + issueKey + "/comment", gson.toJson(new JiraComment(comment)), HTTP_CREATED);
+          .doPost(issueKey + "/comment", gson.toJson(new JiraComment(comment)), HTTP_CREATED);
       log.debug("Comment added to issue {}", issueKey);
     } else {
       log.error("Issue {} does not exist or no access permission", issueKey);
@@ -129,8 +129,7 @@
     log.debug("Transition issue {} to '{}' ({})", issueKey, transition, t.getId());
     return apiBuilder
         .getIssue()
-        .doPost(
-            "/" + issueKey + "/transitions", gson.toJson(new JiraTransition(t)), HTTP_NO_CONTENT);
+        .doPost(issueKey + "/transitions", gson.toJson(new JiraTransition(t)), HTTP_NO_CONTENT);
   }
 
   /** @return Serverinformation of jira */
diff --git a/src/main/java/com/googlesource/gerrit/plugins/its/jira/restapi/JiraRestApi.java b/src/main/java/com/googlesource/gerrit/plugins/its/jira/restapi/JiraRestApi.java
index 9d7589d..aff8428 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/its/jira/restapi/JiraRestApi.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/its/jira/restapi/JiraRestApi.java
@@ -48,7 +48,7 @@
   JiraRestApi(URL url, String user, String pass, Class<T> classOfT, String classPrefix)
       throws MalformedURLException {
     this.auth = Base64.getEncoder().encodeToString((user + ":" + pass).getBytes());
-    this.baseUrl = new URL(url, BASE_PREFIX + classPrefix);
+    this.baseUrl = new URL(url, BASE_PREFIX + classPrefix + "/");
     this.gson = new Gson();
     this.classOfT = classOfT;
   }