Launch screen with bash as shell

Since screen commands are bash specifics make sure we launch screen with
bash login shell instead of other shells.

Fixes bug928883.

Change-Id: I62b4c7182682deb4ef16ed0cf1a3b5a130c1c4ee
diff --git a/stack.sh b/stack.sh
index 00cc1dd..f9ac5ba 100755
--- a/stack.sh
+++ b/stack.sh
@@ -1246,7 +1246,7 @@
 }
 
 # create a new named screen to run processes in
-screen -L -d -m -S stack -t stack
+screen -d -m -S stack -t stack -s /bin/bash
 sleep 1
 # set a reasonable statusbar
 screen -r stack -X hardstatus alwayslastline "%-Lw%{= BW}%50>%n%f* %t%{-}%+Lw%< %= %H"