Increase read time of get datanode test

Build was failing locally for me with development applications open (intellij, chrome, etc...)
After discussion with Toine we are prioritising performance test pipeline with suggested increase from 3.5 seconds to 6 seconds.

Issue-ID: CPS-1171
Signed-off-by: lukegleeson <luke.gleeson@est.tech>
Change-Id: I335fda7ba19b1fb8f4aa543833df65de26d9ccc3
1 file changed