fix elasticsearch default memory consumption

[horahoradev]

CONTAINER ID   NAME                                CPU %     MEM USAGE / LIMIT    MEM %     NET I/O           BLOCK I/O         PIDS
40baac9ba8a9   horahora-frontapi-1                 0.00%     23.4MiB / 30.5GiB    0.07%     574kB / 541kB     18.6MB / 0B       15
cc9a349f062f   d25407b70a5d_horahora-scheduler-1   0.00%     59.69MiB / 30.5GiB   0.19%     78.9MB / 78.5MB   67.2MB / 161MB    29
e8c8f4d56ee1   horahora-videoservice-1             0.01%     80.25MiB / 30.5GiB   0.26%     155MB / 122MB     97.3MB / 289MB    28
a1351597a434   horahora-userservice-1              0.00%     16.29MiB / 30.5GiB   0.05%     468kB / 359kB     12.7MB / 0B       23
10347df4c5f3   horahora-gorse-1                    0.02%     36.07MiB / 30.5GiB   0.12%     259kB / 462kB     8.36MB / 81.9kB   27
3fdb9670880c   horahora-postgres-1                 0.20%     65.05MiB / 30.5GiB   0.21%     791kB / 1.1MB     20.4MB / 27.7MB   14
35ca1cd71814   f78ae7c695e4_horahora-frontend-1    0.00%     84.64MiB / 30.5GiB   0.27%     372kB / 1.02MB    42.6MB / 4.1kB    30
a410ed4e400a   horahora-horaminio-1                0.00%     264.2MiB / 30.5GiB   0.85%     123MB / 348MB     146MB / 124MB     30
50bfb50f73c7   horahora-nginx-1                    0.00%     4.387MiB / 30.5GiB   0.01%     420MB / 420MB     4.5MB / 16.4kB    2
4f7d155b5ed8   horahora-redis-1                    0.09%     5.309MiB / 30.5GiB   0.02%     1.99MB / 844kB    2.24MB / 8.19kB   6
c3d7715ba3dc   horahora-kibana-1                   0.27%     316MiB / 30.5GiB     1.01%     46.5MB / 88.3MB   14.9MB / 2.73MB   12
e3a8fd7fa2e7   horahora-elasticsearch-1            0.13%     15.81GiB / 30.5GiB   51.83%    131MB / 47MB      34.8MB / 1.08GB   188
da52c2055549   horahora-rabbitmq-1                 0.05%     256MiB / 30.5GiB     0.82%     448kB / 139kB     20.4MB / 35.4MB   90

can you spot the outlier? (elasticsearch uses half of the available memory by default)
we should fix this, among other things.