rc: fix rc script parsing

77e1ccbee3ed6c837929e4e232fd07f95bfc8294 introduced a bug whereby
rc scripts in etc/rc.d and $local_startup failed to parse output
from called commands because IFS was set to " " instead of the
default " \t\n". This caused parsing of output that contains any
whitespace character, such as tabs and newlines, not matching just a
space to fail.

PR: 249192
MFC after: 3 weeks
X-MFC with: 77e1ccbee3ed6c837929e4e232fd07f95bfc8294