Remove newlines from wpa_supplicant config network output

Remove newlines from wpa_supplicant config network output

Spurious newlines output while writing the config file can corrupt the
wpa_supplicant configuration. Avoid writing these for the network block
parameters. This is a generic filter that cover cases that may not have
been explicitly addressed with a more specific commit to avoid control
characters in the psk parameter.

Signed-off-by: Paul Stewart <pstew@google.com>