Fix e17 sleeping splash and lingering tempgets.

Fix 2 issues: the e17 splash screen never woke up and stayed on
screen until a timeout. Tempget processes started by the temperature
module, would never exit, when a new instance was spawned (e.g.
after reconfiguring). Both issues had the same cause, and have the
same solution; prefix the command to run with "exec" so that the
shell used to run them is replaced by the new process and the latter
becomes the child process. This was not an issue with bash or zsh,
because these shells seem to automatically exec when called with
-c followed by a simple command. Bump pkgrevision.