use 'exportedPlot' to determine if baseUrl is needed or not

... instead of 'staticPlot', which can conflict when
    users want to draw a 'static plot' in the browser.

Author: etpinard

src/components/drawing/index.js

@@ -1012,7 +1012,7 @@ drawing.setClipUrl = function(s, localId, gd) {
     }
 
     var context = gd._context;
-    var baseUrl = context.staticPlot ? '' : (context.baseUrl || '');
+    var baseUrl = context.exportedPlot ? '' : (context.baseUrl || '');
 
     s.attr('clip-path', 'url(' + baseUrl + '#' + localId + ')');
 };

src/plot_api/to_image.js

@@ -138,6 +138,7 @@ function toImage(gd, opts) {
     // extend config for static plot
     var configImage = Lib.extendFlat({}, config, {
         staticPlot: true,
+        exportedPlot: true,
         setBackground: setBackground
     });
 

test/jasmine/tests/snapshot_test.js

@@ -373,7 +373,7 @@ describe('Plotly.Snapshot', function() {
                 .append('base')
                 .attr('href', 'https://plot.ly');
 
-            Plotly.plot(gd, [{ y: [1, 2, 1] }], {}, {staticPlot: true})
+            Plotly.plot(gd, [{ y: [1, 2, 1] }], {}, {exportedPlot: true})
             .then(function() { return Plotly.Snapshot.toSVG(gd); })
             .then(function(svg) {
                 var svgDOM = parser.parseFromString(svg, 'image/svg+xml');