exec_stmt blocking call.

[acautin]

We stumbled upon a problem when one of the tables was blocked by a non terminated transaction. The call to exec_stmt will never finish
and after login out of dderl ocierl.exe was hanging around even after restarting the service with the table locked (was not able to reproduce that
locally on os x).

I tried creating a table with only one column and then added rows 1 & 2:

OciPort = erloci:new([{logging, true}, {env, [{"NLS_LANG", "GERMAN_SWITZERLAND.AL32UTF8"}]}]).
OciSession = OciPort:get_session(<<"(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=tcp)(HOST=XX.XX.XXX.XXX)(PORT=XXXX)))(CONNECT_DATA=(SERVICE_NAME=XE)))">>,
<<"user">>, <<"pass">>).
CreateTable = <<"create table test (COL1 int)">>.
CreateStmt = OciSession:prep_sql(CreateTable).
CreateStmt:exec_stmt().

Then in 2 separated vms executed:

DeleteRow = <<"delete from test where COL1 = :SOMEVAR">>.
DeleteStmt = OciSession:prep_sql(DeleteRow).
DeleteStmt:bind_vars([{<<":SOMEVAR">>, 'SQLT_STR'}]).
DeleteStmt:exec_stmt([{<<"2">>}],0).

On the first one I got:

(cpro1@127.0.0.1)43> DeleteStmt:exec_stmt([{<<"2">>}],0).
23.11.2016 19:44:30.520476 [debug] [_OCI_] {c_src/erloci_drv/command.cpp,exec_stmt,525} Bounds 
{rowids,[<<"AAAU99AABAAALJxAAA">>]}

But the second one was a blocking call, maybe this is the expected behavior when a transaction can't be completed ?