job-specs: Reduce nr of tests to shorten execution time

Removed tests from iterative job-specs (vpp-mlr-00.md  and vpp-mrr-00.md):
- 2n-clx:
  - IPv4: af-xdp ip4scale-200k, nat44ed udir except 64512 sessions,
  - IPv6: af-xdp ip6scale-200k,
  - l2: af-xdp,
- 2n-skx:
  - IPv4: af-xdp ip4scale-200k, nat44ed udir except 64512 sessions,
  - IPv6: af-xdp ip6scale-200k,
  - L2: af-xdp,
- 2n-zn2:
  - ip4scale-(2m,200k),
  - ip6scale-(2m,200k),
  - l2bdscale-1m,
  - all af-xdp
- 3n-skx:
  - container memif - all
  - ip4scale-(2m,200k,20k),
  - ip6scale-(2m,200k,20k),
  - l2bdscale-(1m,100k,10k),
- 3n-tsh:
  - container memif - all
  - ip4scale-(2m,200k,20k),
  - ip6scale-(2m,200k,20k),
  - l2bdscale-(1m,100k,10k)

Suggestion: Keep coverage job-specs as they are now.

Change-Id: I777f2984b9547406c77d588f663891e9120cf594
Signed-off-by: Tibor Frank <tifrank@cisco.com>