Update border and color of themed input-group-addon and form-control

Override variable in theme does not work because it is imported under
html[theme="default"].

issue9689
review326281002

src/theme.less

@@ -20,11 +20,6 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 */
 
-@input-border-radius: 0;
-@input-border-radius-large: 0;
-@input-border-radius-small: 0;
-@input-bg-disabled: transparent;
-
 .navbar {
     border: none;
     .box-shadow(0 1px 2px rgba(0,0,0,.3));
@@ -93,6 +88,16 @@ THE SOFTWARE.
     }
 }
 
+.form-control {
+    border: transparent;
+
+    &[disabled],
+    &[readonly],
+    fieldset[disabled] & {
+        background-color: transparent;
+    }
+}
+
 textarea,
 textarea.form-control,
 input.form-control,
@@ -140,6 +145,20 @@ input[type=number],
     padding: 0 5px;
 }
 
+.input-group-addon {
+    background-color: transparent;
+    border: transparent;
+    border-radius: 0;
+
+    &.input-sm {
+        border-radius: 0;
+    }
+
+    &.input-lg {
+        border-radius: 0;
+    }
+}
+
 select,
 select.form-control {
     border: 0;