PolyGerrit: Fix changes not loading

We were prefixing the url twice since before we were doing

    _changeBaseURL(changeNum, opt_patchNum) {
      let v = '/changes/' + changeNum;
      if (opt_patchNum) {
        v += '/revisions/' + opt_patchNum;
      }
      return v;
    },

now we are doing

    changeBaseURL(changeNum, patchNum) {
      let v = this.getBaseUrl() + '/changes/' + changeNum;
      if (patchNum) {
        v += '/revisions/' + patchNum;
      }
      return v;
    },

But because the way we were doing it in gr-rest-api, some of the functions
were adding baseUrl allready, so when we called getBaseUrl in changeBaseURL
it was adding it twice.

Change-Id: I2f51fb3ac658ebb659eaf52c858eb113c2f07382

polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.js

diff --git a/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.js b/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.js
index 5bc427b..b130f9a 100644
--- a/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.js
+++ b/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.js
@@ -389,7 +389,7 @@
     },
 
     getChangeActionURL(changeNum, opt_patchNum, endpoint) {
-      return this.changeBaseURL(changeNum, opt_patchNum) + endpoint;
+      return this._changeBaseURL(changeNum, opt_patchNum) + endpoint;
     },
 
     getChangeDetail(changeNum, opt_errFn, opt_cancelCondition) {
@@ -729,7 +729,7 @@
     },
 
     _getDiffFetchURL(changeNum, patchNum, path) {
-      return this.changeBaseURL(changeNum, patchNum) + '/files/' +
+      return this._changeBaseURL(changeNum, patchNum) + '/files/' +
           encodeURIComponent(path) + '/diff';
     },
 
@@ -827,7 +827,7 @@
     },
 
     _getDiffCommentsFetchURL(changeNum, endpoint, opt_patchNum) {
-      return this.changeBaseURL(changeNum, opt_patchNum) + endpoint;
+      return this._changeBaseURL(changeNum, opt_patchNum) + endpoint;
     },
 
     saveDiffDraft(changeNum, patchNum, draft) {
@@ -948,6 +948,14 @@
       });
     },
 
+    _changeBaseURL(changeNum, opt_patchNum) {
+      let v = '/changes/' + changeNum;
+      if (opt_patchNum) {
+        v += '/revisions/' + opt_patchNum;
+      }
+      return v;
+    },
+
     setChangeTopic(changeNum, topic) {
       return this.send('PUT', '/changes/' + encodeURIComponent(changeNum) +
           '/topic', {topic});