Fix parameter format causing duplicate mails

Recently I've experienced mails being duplicated and send to the sender when using the sendmail transport. After consulting my hosting company they told me there shouldn't been a space between "-f" and the envelope sender address. Removing the space character fixed the problem. No more duplicated mails being send to the sender.

Furthermore I tested Swiftmailer and its sendmail transport layer. Absolutely no problems with it.

Looking at the php docs there isn't a space character either, see http://www.php.net/manual/en/function.mail.php#example-3471. Furthermore I found http://stackoverflow.com/questions/4205228/basic-mail-function-php-additional-f-parameter-question and consulted the sendmail docs too: http://www.sendmail.org/~ca/email/man/sendmail.html.

However, there are other examples around with a space character: http://stackoverflow.com/questions/179014/how-to-change-envelope-from-address-using-php-mail. Are they wrong?

Since I'm not familiar with sendmail but actually trusting my hosting company I'm proposing to remove the space character.
Update SendmailTest.php
Merge branch 'patch-1' of github.com:Trainmaster/zf2 into Trainmaster-patch-1
Merge branch 'Trainmaster-patch-1'

Close #6228