increase re-attempt times; introduce more randomness in sleeping time
Merge branch 'MAID-310_improve_concurrent_handling' of github.com:maqi/MaidSafe-Common into MAID-310_improve_concurrent_handling

Conflicts:
	src/maidsafe/common/sqlite3_wrapper.cc
Merge pull request #45 from maqi/MAID-310_improve_concurrent_handling

MAID_310 improve concurrent_handling
Merge branch 'next' of git://github.com/maidsafe/MaidSafe-Common into MAID-423-common_cereal_tests