Fix two minor issues in dynesty printed output

1. Flush the output: neccersery when writing to file
2. Write the total ellapsed time of the run rather than the time since the last checkpoint

changed milestone to %1.2.0

added Bug label

assigned to @colm.talbot

@colm.talbot, when introducing this as standard in bilby_pipe, I noticed these two issues. I assigned you as I think you last modified this bit of the code.

approved this merge request

approved this merge request

added Sampling label

approved this merge request

mentioned in commit ce6caa65

merged

changed milestone to %1.1.5

mentioned in issue bilby_pipe#228 (closed)