Click instead of using ctrl-t for new browser tab

ctrl-t seems to be failing often in Firefox tests, and I can't
figure out why. Let's try clicking the 'new tab' button instead
as a workaround.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

needles/firefox/firefox_new_tab-20190213.json

@@ -0,0 +1,16 @@
+{
+  "area": [
+    {
+      "height": 18,
+      "xpos": 458,
+      "type": "match",
+      "ypos": 73,
+      "width": 16
+    }
+  ],
+  "properties": [],
+  "tags": [
+    "browser_new_tab",
+    "firefox_new_tab"
+  ]
+}

tests/desktop_browser.pm

@@ -23,13 +23,13 @@ sub run {
     wait_idle 5;
     # open a new tab so we don't race with the default page load
     # (also focuses the location bar for us)
-    send_key 'ctrl-t';
+    assert_and_click 'browser_new_tab';
     wait_still_screen 2;
     wait_idle 3;
     # check FAS, typing slowly to avoid errors
     type_very_safely "https://admin.fedoraproject.org/accounts/\n";
     assert_screen "browser_fas_home";
-    send_key 'ctrl-t';
+    assert_and_click 'browser_new_tab';
     wait_still_screen 2;
     wait_idle 2;
     type_very_safely "https://kernel.org\n";
@@ -38,14 +38,14 @@ sub run {
     send_key 'ret';
     # browsers do...something...when the download completes, and we
     # expect there's a single click to make it go away and return
-    # browser to a state where ctrl-t will work
+    # browser to a state where we can open a new tab
     assert_and_click "browser_download_complete";
     # we'll check it actually downloaded later
     # add-on test: at present all desktops we test (KDE, GNOME) are
     # using Firefox by default so we do this unconditionally, but we
     # may need to conditionalize it if we ever test desktops whose
     # default browser doesn't support add-ons or uses different ones
-    send_key 'ctrl-t';
+    assert_and_click 'browser_new_tab';
     wait_still_screen 2;
     wait_idle 2;
     type_very_safely "https://addons.mozilla.org/en-US/firefox/addon/ublock-origin/\n";