agent.sh: Replaced "&>>" redirection by ">> 2>&1"

Replaced to avoid error in old bash(1) versions, since this is somewhat a
new kind of redirection.

Signed-off-by: Erik Alexandre Pucci <eap08@c3sl.ufpr.br>
Signed-off-by: Victor Tarabola Cortiano <vtc10@c3sl.ufpr.br>