Fix SSLSocket NULL pointer deference after close

[cipherboy]

When SSLSocket is closed, the underlying pointer will be immediately
freed and NULLed. This means that any future calls into the native
library could result in a NULL pointer dereference in NSS. This broke
IPA integration tests:

Stack trace of thread 32848:
# - 0  0x00007f362d7aa9e5 raise (libc.so.6 + 0x3c9e5)
# - 1  0x00007f362d793895 abort (libc.so.6 + 0x25895)
# - 2  0x00007f362ca8f4d1 _ZN2os5abortEb.cold (libjvm.so + 0x2114d1)
# - 3  0x00007f362d439a32 _ZN7VMError14report_and_dieEv (libjvm.so + 0xbbba32)
# - 4  0x00007f362d22d934 JVM_handle_linux_signal (libjvm.so + 0x9af934)
# - 5  0x00007f362d2209ac _Z13signalHandleriP9siginfo_tPv (libjvm.so + 0x9a29ac)
# - 6  0x00007f362d7aaa70 __restore_rt (libc.so.6 + 0x3ca70)
# - 7  0x00007f361677a369 Java_org_mozilla_jss_ssl_SSLSocket_shutdownNative (libjss4.so + 0x2c369)
# - 8  0x00007f36187443c7 n/a (n/a + 0x0)

Signed-off-by: Alexander Scheel <ascheel@redhat.com>

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Related: https://pagure.io/dogtagpki/issue/3198

I'm not yet sure what changed between this and N-1 builds.

[jmagne]

This looks quite straightforward. Out of curiosity, do you have a test case for that that demonstrated that this approach fixes it? Although I"m guessing the stack traces you have probably pointed you in this direction. Will approve after comment.

[cipherboy]

@jmagne I have been unable to reproduce the original issue. I'm hoping that if we merge this, we can re-run IPA's nightly tests as usual (but earlier) and confirm that it fixes the reported issue.

[jmagne]

OK, that sounds reasonable, Will approve.

[jmagne]

Unfortunately, the buttons to actually finish off this approval seem to be not present. Therefore just go ahead...

[cipherboy]

ACK, thanks Jack!