Fix late PJSUA2 object destroy on Android

[nanangizz]

audioDevMgr (class DevAudioMedia) is a member of Endpoint, so its destructor is executed after the Endpoint destructor. When the DevAudioMedia destructor invokes AudioMedia::unregisterMediaPort(), exception is triggered when invoking Endpoint::instance(), as the Endpoint::instance_ has been set to NULL, and the exception invokes pj_log() while PJLIB has been deinitialized, so the assertion shown below occurs.

The fix idea is simply to destroy audioDevMgr in Endpoint destructor before Endpoint::instance_ is set to NULL and before PJLIB is deinitialized.

Here is the log and stack trace:

../src/pj/os_core_unix.c:859: pj_thread_t *pj_thread_this(void): assertion "!"Calling pjlib from unknown/external thread. You must " "register external threads with pj_thread_register() " "before calling any pjlib functions."" failed
Fatal signal 6 (SIGABRT), code -1 (SI_QUEUE) in tid 20216 (jsip.pjsua2.app), pid 20216 (jsip.pjsua2.app)
bufferpool2 0x6e6207de28 : 0(0 size) total buffers - 0(0 size) used buffers - 0/4 (recycle/alloc) - 4/35 (fetch/transfer)
evictor expired: 1, evicted: 1
Cmdline: org.pjsip.pjsua2.app
pid: 20216, tid: 20216, name: jsip.pjsua2.app  >>> org.pjsip.pjsua2.app <<<
      #02 pc 00000000006e43e8  libpjsua2.so (pj_thread_this+64) (BuildId: 2aea8bc2d493a43e502575374f5b919687549ac1)
      #03 pc 00000000006f07fc  libpjsua2.so (pj_log+1272) (BuildId: 2aea8bc2d493a43e502575374f5b919687549ac1)
      #04 pc 00000000006f0dec  libpjsua2.so (pj_log_1+160) (BuildId: 2aea8bc2d493a43e502575374f5b919687549ac1)
      #05 pc 0000000000417980  libpjsua2.so (pj::Endpoint::instance()+220) (BuildId: 2aea8bc2d493a43e502575374f5b919687549ac1)
      #06 pc 00000000004376c0  libpjsua2.so (pj::AudioMedia::unregisterMediaPort()+104) (BuildId: 2aea8bc2d493a43e502575374f5b919687549ac1)
      #07 pc 000000000043c918  libpjsua2.so (DevAudioMedia::~DevAudioMedia()+52) (BuildId: 2aea8bc2d493a43e502575374f5b919687549ac1)
      #08 pc 000000000043c99c  libpjsua2.so (DevAudioMedia::~DevAudioMedia()+36) (BuildId: 2aea8bc2d493a43e502575374f5b919687549ac1)
      #09 pc 000000000043ca0c  libpjsua2.so (pj::AudDevManager::~AudDevManager()+64) (BuildId: 2aea8bc2d493a43e502575374f5b919687549ac1)
      #10 pc 0000000000417b50  libpjsua2.so (pj::Endpoint::~Endpoint()+272) (BuildId: 2aea8bc2d493a43e502575374f5b919687549ac1)
      #11 pc 0000000000322224  libpjsua2.so (SwigDirector_Endpoint::~SwigDirector_Endpoint()+88) (BuildId: 2aea8bc2d493a43e502575374f5b919687549ac1)
      #12 pc 000000000032229c  libpjsua2.so (SwigDirector_Endpoint::~SwigDirector_Endpoint()+36) (BuildId: 2aea8bc2d493a43e502575374f5b919687549ac1)
      #13 pc 00000000003ac930  libpjsua2.so (Java_org_pjsip_pjsua2_pjsua2JNI_delete_1Endpoint+64) (BuildId: 2aea8bc2d493a43e502575374f5b919687549ac1)
      #21 pc 000000000002978c  [anon:dalvik-classes2.dex extracted in memory from classes2.dex] (org.pjsip.pjsua2.Endpoint.delete+32)
      #27 pc 000000000000466a  /data/data/org.pjsip.pjsua2.app/code_cache/.overlay/base.apk/classes5.dex (org.pjsip.pjsua2.app.MyApp.deinit+94)
      #33 pc 000000000000341e  /data/data/org.pjsip.pjsua2.app/code_cache/.overlay/base.apk/classes5.dex (org.pjsip.pjsua2.app.MainActivity.handleMessage+14)