Copy m_nice and m_ioprio values from other in ctor

It appears that when commit 201407310b183210ab58b5030abf656e797bae39
added the m_ioprio and m_nice member variables that the
constructor was not updated to copy those values.

Fixes Coverity 1028696

Fixes #11626.

Signed-off-by: Paul Harrison <pharrison@mythtv.org>