Bug 979137 - 1/2: support multiline response of +CGCONTRDP.

For IPV4V6, we're expecting multiple entries for a single PDP
connection:

  +CGCONTRDP: 1,0,"fast.t-mobile.com",<IPv4 address>,...
  +CGCONTRDP: 1,0,"fast.t-mobile.com",<IPv6 address>,...

However, AOSP parcel binding requires all addresses being
concatenated into a SP-separated string.
Bug 979137 - 2/2: allow configuring multiple addresses to an iface.