Use nanosleep instead of pthread_cond_timedwait for thread sleeping

Use nanosleep instead of pthread_cond_timedwait for thread sleeping

There's a comment saying nanosleep's availability is questionable, but
the information of what systems don't have that is now lost in
time. It's quite likely that they were older, Unix systems we no
longer support anyway.

nanosleep comes from POSIX.1b-1993, which is merged into POSIX.1-2001,
so chances are that it's supported almost everywhere where Qt runs
(except for Windows anyway).

Change-Id: I4fd18f8715c43a42429000f3b3d2c3b7343f94b4
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>
Reviewed-by: João Abecasis <joao.abecasis@nokia.com>