Fix Server power operations page style

On the Server power operations page, need a width: 100% for the
"Select a power operation" header.

Drop "Row" from power operations div to fix confirm modal being
cut off.

These are needed because of the move to Bootstrap 4.
84e114a

Resolves openbmc/phosphor-webui#51

Change-Id: I7250daf2aed4ce5af7ed5acdf61a65cc38deac72
Signed-off-by: Gunnar Mills <gmills@us.ibm.com>
diff --git a/app/common/styles/layout/content.scss b/app/common/styles/layout/content.scss
index 5a58478..e50f826 100644
--- a/app/common/styles/layout/content.scss
+++ b/app/common/styles/layout/content.scss
@@ -44,6 +44,7 @@
 }
 
 .subhead {
+  width: 100%;
   border-bottom: 1px solid $medgrey;
   padding-bottom: .5em;
 }