[ENHANCEMENT] Explicitly close FileInputStream

[chibenwa]

I noticed some file descriptors for deleted files:

# lsof -p 1 | grep /tmp
java      1 root  DEL       REG              0,144                   7 /tmp/libnetty_transport_native_epoll_x86_645311867425088058321.so
java      1 root  DEL       REG              0,144                   6 /tmp/jffi8865510689510247619.so
java      1 root  mem-W     REG              0,144     32768         5 /tmp/hsperfdata_root/1
java      1 root  774u     unix 0x0000000000000000       0t0 621499767 /tmp/.java_pid1.tmp type=STREAM
java      1 root  787w      REG              0,144   3022948        16 /tmp/imap-literal11264261390326828628.tmp
java      1 root  934r      REG              0,144    280223         9 /tmp/DelegateCloseableByteSource1691427123218830736.tmp (deleted)
java      1 root  936r      REG              0,144   3666705        11 /tmp/imap-literal9932103542018273411.tmp (deleted)
java      1 root  976r      REG              0,144    207050        12 /tmp/imap-literal1300588447752359868.tmp (deleted)
java      1 root 1021r      REG              0,144   3666705        11 /tmp/imap-literal9932103542018273411.tmp (deleted)
java      1 root 1026r      REG              0,144    207050        12 /tmp/imap-literal1300588447752359868.tmp (deleted)