TCP/TEST: Fix simultaneous ep close with ucp_hello_world

[yosefe]

Why

As a result of #7140, ucp_hello_world fails in docker when it uses TCP transport, like this:

2021-08-10T19:42:56.9329573Z + taskset -c 0 ./examples/ucp_hello_world -f -m host -p 16001
2021-08-10T19:42:56.9651931Z INFO: UCP_HELLO_WORLD mode = 2 server = (null) port = 16001, pid = 20460
2021-08-10T19:43:11.9295628Z + '[' 0 -eq 1 ']'
2021-08-10T19:43:11.9304753Z + client_pid=20476
2021-08-10T19:43:11.9305794Z + wait 20476
2021-08-10T19:43:11.9307301Z + taskset -c 1 ./examples/ucp_hello_world -f -m host -n 0231793f6e3f -p 16001
...
2021-08-10T19:43:12.0205215Z [0231793f6e3f:20476:0:20476]      ucp_ep.c:2822 Assertion `ucp_ep_config(ep)->key.err_mode != UCP_ERR_HANDLING_MODE_NONE' failed
2021-08-10T19:43:12.0206896Z ==== backtrace (tid:  20476) ====
2021-08-10T19:43:12.0208701Z  0  /__w/1/s/build-test/src/ucs/.libs/libucs.so.0(ucs_handle_error+0xfc) [0x7f0a5481f44c]
2021-08-10T19:43:12.0210714Z  1  /__w/1/s/build-test/src/ucs/.libs/libucs.so.0(ucs_fatal_error_message+0x58) [0x7f0a5481c228]
2021-08-10T19:43:12.0212782Z  2  /__w/1/s/build-test/src/ucs/.libs/libucs.so.0(ucs_fatal_error_format+0xd1) [0x7f0a5481c3b1]
2021-08-10T19:43:12.0214903Z  3  /__w/1/s/build-test/src/ucp/.libs/libucp.so.0(ucp_ep_invoke_err_cb+0x1cb) [0x7f0a5450b36b]
2021-08-10T19:43:12.0216926Z  4  /__w/1/s/build-test/src/ucp/.libs/libucp.so.0(ucp_ep_set_failed+0x1f2) [0x7f0a54510102]
2021-08-10T19:43:12.0218867Z  5  /__w/1/s/build-test/src/ucp/.libs/libucp.so.0(+0x4ec2a) [0x7f0a54525c2a]
2021-08-10T19:43:12.0221995Z  6  /__w/1/s/build-test/src/uct/.libs/libuct.so.0(uct_tcp_ep_set_failed+0x61) [0x7f0a542b3cc1]
2021-08-10T19:43:12.0224157Z  7  /__w/1/s/build-test/src/uct/.libs/libuct.so.0(+0x256bf) [0x7f0a542b66bf]
2021-08-10T19:43:12.0225985Z  8  /__w/1/s/build-test/src/uct/.libs/libuct.so.0(+0x29e84) [0x7f0a542bae84]
2021-08-10T19:43:12.0227836Z  9  /__w/1/s/build-test/src/ucs/.libs/libucs.so.0(ucs_event_set_wait+0xf1) [0x7f0a5482ccf1]
2021-08-10T19:43:12.0229713Z 10  /__w/1/s/build-test/src/uct/.libs/libuct.so.0(uct_tcp_iface_progress+0x74) [0x7f0a542bad94]
2021-08-10T19:43:12.0231969Z 11  /__w/1/s/build-test/src/ucp/.libs/libucp.so.0(ucp_worker_progress+0x6a) [0x7f0a54523bca]
2021-08-10T19:43:12.0233840Z 12  /__w/1/s/build-test/examples/.libs/lt-ucp_hello_world() [0x401ed2]
2021-08-10T19:43:12.0235177Z 13  /lib64/libc.so.6(__libc_start_main+0xf5) [0x7f0a53190555]
2021-08-10T19:43:12.0236900Z 14  /__w/1/s/build-test/examples/.libs/lt-ucp_hello_world() [0x402746]
2021-08-10T19:43:12.0238169Z =================================
2021-08-10T19:43:12.0239342Z [0231793f6e3f:20476:0:20476] Process frozen..

(https://dev.azure.com/ucfconsort/0b36e3f0-8ab9-4a48-b68b-4b2350e02c88/_apis/build/builds/22781/logs/389)

How

• UCP: Don't try to invoke error callback if endpoint closed but not flushed yet. If user started to close endpoint, callbacks should not be called on this endpoint anymore. This change avoids the assert fail above.
• TCP: Flush outstanding put operations in case of error. Without this change, endpoint close (flush stage) does not finish.
• Test: run ucp_hello_world with TCP

[yosefe]

@dmitrygx @evgeny-leksikov can you pls take a look?

[yosefe]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

[yosefe]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

[yosefe]

@hoopoepg can you pls review latest commit ? i saw you added this line but maybe there was another intention i missed

[yosefe]

bot:pipe:retest