Fix: ping: Correctly advertise multiplier default

Advertise the multiplier default value in the meta data.
Low: ping: Add use_fping parameter

Add parameter that allows control over which ping
binary is used. If set to 0, fping will not be used,
instead ping is used even if fping is available.
Low: ping: Remove incorrectly advertised migrate_to|migrate_from
Low: ping: Pass extra options to fping
Low: ping: Correct metadata for attempts parameter
Merge pull request #590 from krig/ping-fixes

Fixes to the ping RA (bnc#899324)