BUG #16160: Minor memory leak in case of starting postgres server with SSL encryption

The following bug has been logged on the website:

Bug reference:      16160
Logged by:          Dmitry Uspenskiy
Email address:      duspensky@ya.ru
PostgreSQL version: 12.1
Operating system:   Any
Description:

LeakSanitizer shows memory leak at the following place:

[ts-1] ==17346==ERROR: LeakSanitizer: detected memory leaks
[ts-1] 
[ts-1] Direct leak of 144 byte(s) in 1 object(s) allocated from:
[ts-1]     #0 0x563b7f in __interceptor_malloc
/home/duspensky/code/yugabyte-db/thirdparty/build/common/llvm-7.0.1.src/../../../src/llvm-7.0.1.src/projects/comp
iler-rt/lib/asan/asan_malloc_linux.cc:146
[ts-1]     #1 0x7f697e6a7ee7 in CRYPTO_malloc
(/home/duspensky/.linuxbrew-yb-build/linuxbrew-20181203T161736/lib/libcrypto.so.1.0.0+0x71ee7)
[ts-1]     #2 0x7f697e746b2e in DH_new_method
(/home/duspensky/.linuxbrew-yb-build/linuxbrew-20181203T161736/lib/libcrypto.so.1.0.0+0x110b2e)
[ts-1]     #3 0x7f697e74609c in dh_cb
(/home/duspensky/.linuxbrew-yb-build/linuxbrew-20181203T161736/lib/libcrypto.so.1.0.0+0x11009c)
[ts-1]     #4 0x7f697e78a1fc in ASN1_item_ex_new
(/home/duspensky/.linuxbrew-yb-build/linuxbrew-20181203T161736/lib/libcrypto.so.1.0.0+0x1541fc)
[ts-1]     #5 0x7f697e78f09a in ASN1_item_ex_d2i
(/home/duspensky/.linuxbrew-yb-build/linuxbrew-20181203T161736/lib/libcrypto.so.1.0.0+0x15909a)
[ts-1]     #6 0x7f697e78f7ba in ASN1_item_d2i
(/home/duspensky/.linuxbrew-yb-build/linuxbrew-20181203T161736/lib/libcrypto.so.1.0.0+0x1597ba)
[ts-1]     #7 0x7f697e7a0ad3 in PEM_read_bio_DHparams
(/home/duspensky/.linuxbrew-yb-build/linuxbrew-20181203T161736/lib/libcrypto.so.1.0.0+0x16aad3)
[ts-1]     #8 0xcd75bd in load_dh_buffer

/home/duspensky/code/yugabyte-db/src/postgres/src/backend/libpq/../../../../../../src/postgres/src/backend/libpq/be-secure-openssl.c:848:7
[ts-1]     #9 0xcd4d07 in initialize_dh

/home/duspensky/code/yugabyte-db/src/postgres/src/backend/libpq/../../../../../../src/postgres/src/backend/libpq/be-secure-openssl.c:976:8
[ts-1]     #10 0xcd437c in be_tls_init

/home/duspensky/code/yugabyte-db/src/postgres/src/backend/libpq/../../../../../../src/postgres/src/backend/libpq/be-secure-openssl.c:198:7
[ts-1]     #11 0xeecd86 in PostmasterMain

/home/duspensky/code/yugabyte-db/src/postgres/src/backend/postmaster/../../../../../../src/postgres/src/backend/postmaster/postmaster.c:981:10
[ts-1]     #12 0xcd79e3 in PostgresServerProcessMain

/home/duspensky/code/yugabyte-db/src/postgres/src/backend/main/../../../../../../src/postgres/src/backend/main/main.c:234:3
[ts-1]     #13 0xcd8081 in main
(/home/duspensky/code/yugabyte-db/build/asan-clang-dynamic-ninja/postgres/bin/postgres+0xcd8081)

According to the following information

https://wiki.openssl.org/index.php/Diffie-Hellman_parameters

DH_free function must be called after SSL_CTX_set_tmp_dh