Fix sendCommand line splitup for some imap proxys

When sending a command it would be sent like this:
PKG1: 1 STARTTLS
PKG2: \r\n

Some imap proxys (maybe from Fortinet?) don't accept commands across packets:
PKG1: 1 STARTTLS\r\n
Merge pull request #456 from asdil12/single_pkg_command

Fix sendCommand line splitup