"core": vbash should not modify $PATH

This CL updates vbash so that it does not modify $PATH

Change-Id: I8fe1650a08df3b3501b90a70ff4b47b91fc96cae
diff --git a/tools/mgmt/vbash b/tools/mgmt/vbash
index ea5047f..92c5c4d 100755
--- a/tools/mgmt/vbash
+++ b/tools/mgmt/vbash
@@ -191,7 +191,6 @@
 default_blessing() {
   "${BIN_INSTALL}/principal" dump | grep "Default blessings" | sed -e 's/Default blessings: //'
 }
-export PATH="${PATH}:${BIN_INSTALL}"
 export PS1="\${PS1}(\${GREENBOLD}\$(default_blessing)\[\033[0m\])$ "
 EOF