Correct tcp_not_use_nodelay option processing - change in mca param system incorrectly reversed the original parameter

Thanks to Tetsuya Mishima for detecting it!

cmr=v1.7.4:reviewer=jsquyres:subject=Correct tcp_not_use_nodelay option processing
Ensure comm_spawn'd jobs get treated the same wrt setting default mapping directives

Refs #4059
Initialize variable so dash-host option gets correctly parsed

cmr=v1.7.4:reviewer=rolfv