Check cache options for NFS since it's giving false positives since the scheduled `git gc` actions

Since the scheduled git gc feature we see some false positives file lookup issues on NFS caused by NFS caching.

Let's see if we can tweak the cache options on NFS a bit better.

I will use this command to check TTFB and verify NFS cache speeds:

jeroen@xps15:~$ for x in `seq 1 5`;do curl -o /dev/null -w "Connect: %{time_connect} TTFB: %{time_starttransfer} Total time: %{time_total} \n" -s https://gitlab.com/gitlab-org/gitlab-ce/tree/master; done
Connect: 0.108 TTFB: 3.659 Total time: 3.754 
Connect: 0.107 TTFB: 3.207 Total time: 3.301 
Connect: 0.111 TTFB: 3.617 Total time: 3.716 
Connect: 0.106 TTFB: 3.031 Total time: 3.125 
Connect: 0.106 TTFB: 2.494 Total time: 2.588