fix(card): Image selector should only select immediate children or images within md-card-header

Closes angular#8785

Closes angular#8786

Author: epelc

src/components/card/card.scss

@@ -60,7 +60,7 @@ md-card {
   }
 
   > img,
-  > :not(md-card-content) img {
+  > md-card-header img {
     box-sizing: border-box;
     display: flex;
     flex: 0 0 auto;