Fix parsing perf regression
Fix parsing perf regression

Summary:
bhosmer noted that {D2792581} caused a perf regression in parsing.
After investigating I noticed that Flow really was parsing twice as many files
(avikchaudhuri was right) though it merges them into a set afterwards, so it doesn't
infer twice as many.

The cause of the diff was that the new find code doesn't put `/` at the end of
directories. This broke some code that checked to see if a directory was a
symlink. It would incorrectly conclude that every directory contained a symlink
and then would start over again with a better path filter.

Reviewed By: bhosmer

Differential Revision: D2873888

fb-gh-sync-id: 287b59f65b20ccfe659f6edb87aa41a10b4d35bc

jgrund/flow,d14b3l/flow,samwgoldman/flow,ylu1317/flow,popham/flow,facebook/flow,MichaelDeBoey/flow,ForbesLindesay/flow,cesarandreu/flow,samwgoldman/flow,shiftcars/flow,AgentME/flow,jdelStrother/flow,graue/flow,fletcherw/flow,claudiopro/flow,mroch/flow,shiftcars/flow,jamesgpearce/flow,facebook/flow,ylu1317/flow,fletcherw/flow,mroch/flow,AgentME/flow,samwgoldman/flow,MichaelDeBoey/flow,shiftcars/flow,JonathanUsername/flow,MichaelDeBoey/flow,JonathanUsername/flow,mroch/flow,ForbesLindesay/flow,claudiopro/flow,gabelevi/flow,jdelStrother/flow,AgentME/flow,facebook/flow,d14b3l/flow,TiddoLangerak/flow,fletcherw/flow,AprilArcus/flow,jgrund/flow,ylu1317/flow,d14b3l/flow,JonathanUsername/flow,claudiopro/flow,jeffmo/flow,graue/flow,JonathanUsername/flow,jeffmo/flow,nmote/flow,gabro/flow,popham/flow,mroch/flow,AgentME/flow,claudiopro/flow,gabelevi/flow,jamesgpearce/flow,gabro/flow,TiddoLangerak/flow,chenglou/flow,mroch/flow,gabelevi/flow,AprilArcus/flow,popham/flow,jgrund/flow,ForbesLindesay/flow,shiftcars/flow,jgrund/flow,jeffmo/flow,cesarandreu/flow,AprilArcus/flow,jamesgpearce/flow,jdelStrother/flow,cesarandreu/flow,ForbesLindesay/flow,MichaelDeBoey/flow,gabro/flow,d14b3l/flow,mroch/flow,TiddoLangerak/flow,nmote/flow,gabro/flow,AprilArcus/flow,graue/flow,d14b3l/flow,popham/flow,mroch/flow,samwgoldman/flow,fletcherw/flow,gabelevi/flow,gabro/flow,jdelStrother/flow,shiftcars/flow,graue/flow,jdelStrother/flow,samwgoldman/flow,nmote/flow,jgrund/flow,AprilArcus/flow,MichaelDeBoey/flow,samwgoldman/flow,JonathanUsername/flow,gabelevi/flow,chenglou/flow,d14b3l/flow,facebook/flow,chenglou/flow,jeffmo/flow,nmote/flow,jamesgpearce/flow,ForbesLindesay/flow,TiddoLangerak/flow,fletcherw/flow,graue/flow,nmote/flow,ForbesLindesay/flow,TiddoLangerak/flow,nmote/flow,AgentME/flow,nmote/flow,samwgoldman/flow,claudiopro/flow,popham/flow,jeffmo/flow,JonathanUsername/flow,gabro/flow,facebook/flow,graue/flow,jgrund/flow,gabelevi/flow,jamesgpearce/flow,facebook/flow,AprilArcus/flow,jamesgpearce/flow,gabelevi/flow,chenglou/flow,jdelStrother/flow,chenglou/flow,fletcherw/flow,ylu1317/flow,JonathanUsername/flow,shiftcars/flow,jamesgpearce/flow,ylu1317/flow,popham/flow,popham/flow,chenglou/flow,cesarandreu/flow,jeffmo/flow,facebook/flow