Fix Github auto-build

[abitmore]

Remove the predefined boost related environment variables.

Follow-up work of #2062 for issue #2054.

See also: #2110.

Errors (also mentioned in #2062):

• The es_tests still seem to be not completely deterministic, see Fix Github auto-build #2112 (comment).
• The failing "Node Test" in native mac and Ubuntu build is due to remove custom operation plugin check from custom api creation #2033 not yet being in develop.

[abitmore]

Errors:

Release:

64850ms th_a elasticsearch_plugin.cpp:516 plugin_startup ] elasticsearch ACCOUNT HISTORY: plugin_startup() begin
69440ms th_a main.cpp:127 test_method ] e.to_detail_string(): 6 key_not_found_exception: Key Not Found
Key _source
{"key":"_source"}
th_a variant_object.cpp:90 operator[]
69441ms th_a db_management.cpp:243 close ] Rewinding from 5 to 0
69441ms th_a db_management.cpp:253 close ] Database close unexpected exception: {"code":10,"name":"assert_exception","message":"Assert Exception","stack":[{"context":{"level":"error","file":"fork_database.cpp","line":41,"method":"pop_block","hostname":"","thread_name":"th_a","timestamp":"2020-02-25T00:01:09"},"format":"prev: popping block would leave head block null","data":{}},{"context":{"level":"warn","file":"db_block.cpp","line":518,"method":"pop_block","hostname":"","thread_name":"th_a","timestamp":"2020-02-25T00:01:09"},"format":"","data":{}}]}

*** 4 failures are detected in the test module "Elastic Search Database Tests"
Running 1 test case...
/home/runner/work/bitshares-core/bitshares-core/tests/elasticsearch/main.cpp(80): error: in "elasticsearch_tests/elasticsearch_account_history": check total == "5" has failed [0 != 5]

---

Debug:

3523467ms th_a elasticsearch_plugin.cpp:516 plugin_startup ] elasticsearch ACCOUNT HISTORY: plugin_startup() begin
3528319ms th_a main.cpp:127 test_method ] e.to_detail_string(): 6 key_not_found_exception: Key Not Found
Key _source
{"key":"_source"}
th_a variant_object.cpp:90 operator[]
3528319ms th_a db_management.cpp:243 close ] Rewinding from 5 to 0
3528319ms th_a db_management.cpp:253 close ] Database close unexpected exception: {"code":10,"name":"assert_exception","message":"Assert Exception","stack":[{"context":{"level":"error","file":"fork_database.cpp","line":41,"method":"pop_block","hostname":"","thread_name":"th_a","timestamp":"2020-02-24T23:58:48"},"format":"prev: popping block would leave head block null","data":{}},{"context":{"level":"warn","file":"db_block.cpp","line":518,"method":"pop_block","hostname":"","thread_name":"th_a","timestamp":"2020-02-24T23:58:48"},"format":"","data":{}}]}

*** 2 failures are detected in the test module "Elastic Search Database Tests"
/home/runner/work/bitshares-core/bitshares-core/tests/elasticsearch/main.cpp(113): error: in "elasticsearch_tests/elasticsearch_account_history": check total == "13" has failed [0 != 13]
unknown location(0): fatal error: in "elasticsearch_tests/elasticsearch_account_history": unknown type
/home/runner/work/bitshares-core/bitshares-core/tests/elasticsearch/main.cpp(113): last checkpoint

[abitmore]

Fixed es_test in this PR. Will fix "Node Test" in #2169.