make tests allocate much less memory

it was getting in the way of doing proper analysis
new attempt/approach at verifying all received records with less allocations

as you can see, i couldn't make it work (esp at step 3 it gets tricky)
so disabled for now.  anyway with the previous approach all these checks
were fine, so it'll still be fine, and we check the num received anyway.
but we should try to reintroduce these checks somehow
this implementation should do less/smaller memory allocations

actually it's not the case, so i'm reverting it straight away.
but i feel like it's good to have this in the git history for reference

tested by sending and receiving 100k messages

BEFORE

    5002398987 ns/op
ok  github.com/graphite-ng/carbon-relay-ng  5.011s

AFTER

after:
    15001749641 ns/op
ok  github.com/graphite-ng/carbon-relay-ng 5.015s

BEFORE MEM
(pprof) top40
Total: 11.8 MB
     4.6  38.7%  38.7%      4.6  38.7% github.com/graphite-ng/carbon-relay-ng.NewKeepSafe
     4.5  38.0%  76.6%      4.5  38.0% github.com/graphite-ng/carbon-relay-ng.(*TestEndpoint).handle
     2.3  19.1%  95.8%      2.3  19.1% github.com/graphite-ng/carbon-relay-ng.func·009
     0.5   4.2% 100.0%      0.5   4.2% allocg
     0.0   0.0% 100.0%      0.5   4.2% _rt0_go
     0.0   0.0% 100.0%      4.6  38.7% github.com/graphite-ng/carbon-relay-ng.(*Destination).updateConn
     0.0   0.0% 100.0%      4.6  38.7% github.com/graphite-ng/carbon-relay-ng.NewConn
     0.0   0.0% 100.0%      0.5   4.2% mcommoninit
     0.0   0.0% 100.0%     11.3  95.8% runtime.gosched0
     0.0   0.0% 100.0%      0.5   4.2% runtime.malg
     0.0   0.0% 100.0%      0.5   4.2% runtime.mpreinit
     0.0   0.0% 100.0%      0.5   4.2% runtime.schedinit

AFTER MEM
(pprof) top100
Total: 18.3 MB
     6.0  32.8%  32.8%      6.0  32.8% container/list.(*List).insertValue
     5.0  27.4%  60.2%      5.0  27.4% github.com/graphite-ng/carbon-relay-ng.(*TestEndpoint).handle
     3.5  19.2%  79.4%      3.5  19.2% runtime.convT2E
     2.3  12.4%  91.8%      2.3  12.4% github.com/graphite-ng/carbon-relay-ng.func·010
     0.5   2.7%  94.5%      0.5   2.7% allocg
     0.5   2.7%  97.3%      0.5   2.7% hash/crc32.makeTable
     0.5   2.7% 100.0%      0.5   2.7% time.loadZoneData

BEFORE CPU:
(pprof) top100
Total: 259 samples
      50  19.3%  19.3%       50  19.3% runtime.futex
      14   5.4%  24.7%       14   5.4% runtime.xchg
      12   4.6%  29.3%       30  11.6% runtime.mallocgc
      10   3.9%  33.2%       31  12.0% selectgo
       9   3.5%  36.7%        9   3.5% runtime.usleep
       7   2.7%  39.4%        7   2.7% scanblock
       5   1.9%  41.3%        5   1.9% runtime.memclr
       5   1.9%  43.2%        5   1.9% stopm
       4   1.5%  44.8%       12   4.6% cnew
       4   1.5%  46.3%        7   2.7% fmt.(*pp).printArg
       4   1.5%  47.9%        4   1.5% runtime.MSpan_Sweep
       4   1.5%  49.4%        4   1.5% runtime.epollwait
       4   1.5%  51.0%        9   3.5% runtime.lock

AFTER CPU:

      55  19.6%  19.6%       55  19.6% runtime.futex
      13   4.6%  24.2%       13   4.6% flushptrbuf
      13   4.6%  28.8%       31  11.0% runtime.mallocgc
      12   4.3%  33.1%       30  10.7% selectgo
       9   3.2%  36.3%        9   3.2% scanblock
       8   2.8%  39.1%        8   2.8% runtime.MSpan_Sweep
       8   2.8%  42.0%        8   2.8% runtime.usleep
       7   2.5%  44.5%        7   2.5% runtime.xchg
       6   2.1%  46.6%        6   2.1% ExternalCode
       6   2.1%  48.8%        6   2.1% schedule
       5   1.8%  50.5%       29  10.3% github.com/graphite-ng/carbon-relay-ng.(*Conn).HandleData
       5   1.8%  52.3%       40  14.2% github.com/graphite-ng/carbon-relay-ng.(*Destination).relay
Revert "this implementation should do less/smaller memory allocations"

This reverts commit ce58c37b14bb11af20ad20c4816c2e61b5b876e1.