beta-code-update: use mwdeploy home for wmf-beta-autoupdate

The wmf-beta-autoupdate runs npm
https://gerrit.wikimedia.org/r/#/c/93939/ and since it attempts to write
in the $HOME dir, it better has to be set to the home of the mwdeploy
user. sudo -H achieve that.

Change-Id: I4626d76ad268374dfc7f9a1306512c3a9108df32