Solve problem with deadlocks in iterators

[ShunkevichDV]

When several agents work with the same sc-element, a deadlock is likely to occur

Possibly the problem (or one of them) is somewhere in sc_iterator...._next functions

https://github.com/ostis-dev/sc-machine/blob/master/sc-memory/sc-core/sc-store/sc_iterator3.c

[ShunkevichDV]

Possibly same issue with #267

[Vikort]

sc-machine deadlock test

https://github.com/Vikort/sc-machine/tree/bug/sc-machine-deadlock-test

To run tests

• Clone repository

  git clone https://github.com/Vikort/sc-machine.git
  cd sc-machine
  git checkout bug/sc-machine-deadlock-test
  git submodule update --init --recursive

• Build sc-machine

  In sc-machine folder

  mkdir build
  cd build
  cmake ..
  make

• Run

  In sc-machine folder

  cd bin
  ./sc-machine-deadlock