Merge pull request #1699 from mattermost/plt-1455

PLT-1455 Fixing jumping of center channel with few posts on IE11

web/sass-files/sass/partials/_post.scss

@@ -209,6 +209,7 @@ body.ios {
 	@include flex(1 1 auto);
 	position: relative;
 	overflow-y: hidden;
+	height: 100%;
 
 	.post-list-holder-by-time {
 		background: #fff;