Solves regression: not waiting after command.

A regression was inadvertently introduced in commit:
Implemented return to same-current task on system call or task error.
(31d8a59481c3fa558c33da7a9cbe33e9ce720da8)  Tue Apr 23 13:29:31 2013

Program not waiting after a succesful command. Conditional block
    if ( $retval != 0 ) { # system returned an error
erroneously included     print($STRING_MSG_RET); <STDIN>;
Merge branch 'regresswait'