Update git submodules

Update git submodules

* Update docs/submodules/storperf from branch 'stable/euphrates'
  - Merge "Resolve error in fetching metrics" into stable/euphrates
  - Resolve error in fetching metrics

    There seems to be an update in the json format used.
    The data is present at ['details']['metrics'] rather
    than ['metrics']

    JIRA: STORPERF-229

    Change-Id: I7c3ee319ef4a128c33f5e2a26e10b6ff03a471d3
    Signed-off-by: Shrenik <shrenik.jain@research.iiit.ac.in>
    (cherry picked from commit f5759099c69e1885ea72ff1e75794101b179eeac)