Fix incorrect use of "skip" parameter to configureFailPoint in txn_two_phase_commit_failover.js

1) Specify "skip" as the "mode" parameter, not as a separate field

2) For the test cases where the config server is the coordinator, if "skip" is specified, increment "skip" in addition to "numTimesShouldBeHit"

3) This line should probably go inside the if block above it for all the coordinator failpoints, otherwise I think the skip will be incremented twice, once for the if-condition and once on that line.