Fix SELinux get.. methods aborting on invalid address

SELinux get.. JNI need the 'security_context_t tmp' entries set
to NULL, otherwise on error freecon() tries to release uninitialised
memory causing apps to abort with invalid address.
Also fixed getPeerCon ALOGV call as this caused Zyote to abort when
verbose logging set.

Signed-off-by: Richard Haines <richard_c_haines@btinternet.com>