Setting error injections via environment variables.

It is possible to set errinjs using environment variables(further just env). Create env with the same name as error injection name in errinj.h (e.g.: ERRINJ_TESTING, ERRINJ_WAL_IO and etc.) and assign it to a value satisfied to such rules:

• For boolean error injections "true" or "false" in any case;
• For integer error injections it should be an integer number ("2", "-3" and etc.);
• For double error injections it should be a float number with decimal point as '.' ("2.45", "-2.45");

If value of env breaks the rules above then tarantool will report it and exit.

NOTE: This function works only in Debug version as error injections at all.

Examples:

• Correct names:

$ ERRINJ_TESTING=True ERRINJ_WAL_WRITE_PARTIAL=1 ERRINJ_RELAY_TIMEOUT=2.3 tarantool
Tarantool 2.8.0-104-ga801f9f35
type 'help' for interactive help
tarantool> box.error.injection.get('ERRINJ_TESTING')
---
- true
...

tarantool> box.error.injection.get('ERRINJ_WAL_WRITE_PARTIAL')
---
- 1
...

tarantool> box.error.injection.get('ERRINJ_RELAY_TIMEOUT')
---
- 2.3
...

• Incorrect names:

$ ERRINJ_WAL_WRITE_PARTIAL=1e10 tarantool
Incorrect value for integer ERRINJ_WAL_WRITE_PARTIAL: 1e10
$ ERRINJ_RELAY_TIMEOUT=2,3 tarantool
Incorrect value for double ERRINJ_RELAY_TIMEOUT: 2,3
$ ERRINJ_TESTING=Tru tarantool       
Incorrect value for boolean ERRINJ_TESTING: Tru