They were planned separately.
It takes a long time to plan and execute a launch, and both Antares ORB-3 and Progress M-25M had their launch dates set months ago.
To see how far ahead some of these launches are planned look at: http://www.spaceflightnow.com/tracking/
For instance in August next year Progress 60P and SpaceX CRS-8 will also launch within a week of each other.
 As TildalWave points out below, these are only tentative launch dates. In fact ORB-3 was initially scheduled to launch the day before it did, but was scrubbed for range safety issues (a boat failed to clear the exclusion zone).
The ISS is currently supplied (or was) by the following vehicles:
- Space Shuttle - retired
- ESA Automated Transfer Vehicle (ATV) - last one has flown - retired
- JAXA H2 Transfer Vehicle (HTV) - which has only a few flights left before retirement
- Russian Progress - cargo, fuel, air, water - active
- Russian Soyuz - crew, very minimal cargo
- US SpaceX Dragon - contract for 12 flights, second contract for future flights is being worked out. Only remaining vehicle that return cargo to Earth.
- US Orbital Sciences Cygnus- Contract for 8 flights, failure on 4th mission. Possible competitor for second cargo contract.
The schedule for all these vehicles is planned by the ISS team and is very complicated and interlocking. Each is given a window of time at the station that allows for crew time to load/unload them after the berth/dock. Some (HTV, Cygnus, Dragon) share ports and thus can conflict. ATV, Soyuz, and Progress all share the same docking systems, but there are 4 such ports available so they conflict less.
Thus the short answer is that the Progress flight was completely independent of the Cygnus launch, except that the timing was planned so as not to have concurrent docking operations using up needed crew time to process them.