DB doesn't properly close if main process fails

[rebeccabilbro]

If the process fails or is interrupted, the leveldb database doesn't get closed properly and can cause and error on the next run.

2020/04/10 08:34:24 connected to s3
panic: Could not open manifest

goroutine 1 [running]:
github.com/kansaslabs/baleen/store.MustOpen(...)
	/Users/rebeccabilbro/Desktop/eudicot/goplaces/src/github.com/kansaslabs/baleen/store/manifest.go:12
main.run(0xc000246160, 0x0, 0x0)
	/Users/rebeccabilbro/Desktop/eudicot/goplaces/src/github.com/kansaslabs/baleen/cmd/baleen/main.go:107 +0x150a
github.com/kansaslabs/baleen/vendor/gopkg.in/urfave/cli%2ev1.HandleAction(0x1699560, 0x17d6108, 0xc000246160, 0xc000240000, 0x0)
	/Users/rebeccabilbro/Desktop/eudicot/goplaces/src/github.com/kansaslabs/baleen/vendor/gopkg.in/urfave/cli.v1/app.go:490 +0xc8
github.com/kansaslabs/baleen/vendor/gopkg.in/urfave/cli%2ev1.Command.Run(0x178483e, 0x3, 0x0, 0x0, 0x0, 0x0, 0x0, 0x179b0fa, 0x20, 0x0, ...)
	/Users/rebeccabilbro/Desktop/eudicot/goplaces/src/github.com/kansaslabs/baleen/vendor/gopkg.in/urfave/cli.v1/command.go:210 +0x996
github.com/kansaslabs/baleen/vendor/gopkg.in/urfave/cli%2ev1.(*App).Run(0xc00022e000, 0xc00000e080, 0x2, 0x2, 0x0, 0x0)
	/Users/rebeccabilbro/Desktop/eudicot/goplaces/src/github.com/kansaslabs/baleen/vendor/gopkg.in/urfave/cli.v1/app.go:255 +0x6af
main.main()
	/Users/rebeccabilbro/Desktop/eudicot/goplaces/src/github.com/kansaslabs/baleen/cmd/baleen/main.go:46 +0x18c