Fix bug in JetPlayer::loadFromFile

A long pathname would corrupt the heap due to incorrect use of strncpy.

Also was using hard-coded constant 256 instead of PATH_MAX.

Change-Id: Iba382bbb38624fbc41fec91449f9814f77d4ac0d
diff --git a/media/libmedia/JetPlayer.cpp b/media/libmedia/JetPlayer.cpp
index 188e582..38f05f2 100644
--- a/media/libmedia/JetPlayer.cpp
+++ b/media/libmedia/JetPlayer.cpp
@@ -338,8 +338,8 @@
     Mutex::Autolock lock(mMutex);
 
     mEasJetFileLoc = (EAS_FILE_LOCATOR) malloc(sizeof(EAS_FILE));
-    memset(mJetFilePath, 0, 256);
-    strncpy(mJetFilePath, path, strlen(path));
+    strncpy(mJetFilePath, path, sizeof(mJetFilePath));
+    mJetFilePath[sizeof(mJetFilePath) - 1] = '\0';
     mEasJetFileLoc->path = mJetFilePath;
 
     mEasJetFileLoc->fd = 0;