test_irepl_multithreaded fails when python is the default rule engine instance

[rskarbez]

 --- IrodsSession: icommand executed by [otherrods] [iput largefile.txt] --- 
Assert Command: iput largefile.txt
Expecting EMPTY: ['']
  stdout:
    | 
  stderr:
    | remote addresses: 127.0.0.1 ERROR: rcvTranHeader: toread = 24, read = 0
    |  ERROR: rcvTranHeader: toread = 24, read = 0
    |  ERROR: rcvTranHeader: toread = 24, read = 0
    |  ERROR: rcvTranHeader: toread = 24, read = 0
    |  ERROR: rcvTranHeader: toread = 24, read = 0
    |  ERROR: rcvTranHeader: toread = 24, read = 0
    |  ERROR: rcvTranHeader: toread = 24, read = 0
    |  ERROR: rcvTranHeader: toread = 24, read = 0
    |  ERROR: rcvTranHeader: toread = 24, read = 0
    |  ERROR: rcvTranHeader: toread = 24, read = 0
    |  ERROR: rcvTranHeader: toread = 24, read = 0
    |  ERROR: rcvTranHeader: toread = 24, read = 0
    |  ERROR: rcvTranHeader: toread = 24, read = 0
    |  ERROR: rcvTranHeader: toread = 24, read = 0
    |  ERROR: rcvTranHeader: toread = 24, read = 0
    |  ERROR: rcvTranHeader: toread = 24, read = 0
    |  ERROR: [-]	/home/rskarbez/software/irods/lib/core/src/procApiRequest.cpp:176:int sendApiRequest(rcComm_t *, int, void *, bytesBuf_t *) :  status [SYS_HEADER_WRITE_LEN_ERR]  errno [Broken pipe] -- message []
    | 	[-]	/home/rskarbez/software/irods/lib/core/src/sockComm.cpp:1258:irods::error sendRodsMsg(irods::network_object_ptr, const char *, bytesBuf_t *, bytesBuf_t *, bytesBuf_t *, int, irodsProt_t) :  status [SYS_HEADER_WRITE_LEN_ERR]  errno [Broken pipe] -- message [failed to call 'write body']
    | 		[-]	/home/rskarbez/software/irods/plugins/network/tcp/libtcp.cpp:355:irods::error tcp_send_rods_msg(irods::plugin_context &, const char *, bytesBuf_t *, bytesBuf_t *, bytesBuf_t *, int, irodsProt_t) :  status [SYS_HEADER_WRITE_LEN_ERR]  errno [Broken pipe] -- message [writeMsgHeader failed]
    | 			[-]	/home/rskarbez/software/irods/lib/core/src/sockComm.cpp:475:irods::error writeMsgHeader(irods::network_object_ptr, msgHeader_t *) :  status [SYS_HEADER_WRITE_LEN_ERR]  errno [Broken pipe] -- message []
    | 				[-]	/home/rskarbez/software/irods/plugins/network/tcp/libtcp.cpp:293:irods::error tcp_write_msg_header(irods::plugin_context &, bytesBuf_t *) :  status [SYS_HEADER_WRITE_LEN_ERR]  errno [Broken pipe] -- message [wrote 0 expected 139]
    | 
    |  ERROR: putUtil: put error for /tempZone/home/otherrods/2016-11-22Z22:49:49--irods-testing-rteRDg/largefile.txt, status = -27000 status = -27000 SYS_COPY_LEN_ERR
Unexpected output on stderr

FAILED TESTING ASSERTION

[rskarbez]

The problem was that large file puts spawn multiple threads to handle them, each of which can generate peps. This caused contention on the Python interpreter, and ultimately segfaults.

Resolved by putting calls that access the Python interpreter inside a mutex.