Future-proof fusermount{3, 4, 5,...} call

[probonopd]

Current behavior:

• Check for fusermount3,
• Fall back to fusermount

Suggested behavior:

• Check for fusermountN with N= any integer and use the highest one
• fall back to fusermount

Advantage:
Exisitng binaries will continue to work once there will be fusermount4 instead of fusermount3.

go-fuse/fuse/mount_linux.go

Lines 225 to 232 in 934a183

	// fusermountBinary returns the path to the `fusermount3` binary, or, if not
	// found, the `fusermount` binary.
	func fusermountBinary() (string, error) {
	if path, err := lookPathFallback("fusermount3", "/bin"); err == nil {
	return path, nil
	}
	return lookPathFallback("fusermount", "/bin")
	}

References:

• fusermount, fusermount3,... fusermountN compatibility guarantees?  libfuse/libfuse#670
• Statically linked runtime AppImage/AppImageKit#877
• Remove the need for fusermount probonopd/static-appimage#4

[hanwen]

If fusermount4 introduces a new calling convention (typically, this is what you introduce a new version number for!), then this would fail in mysterious ways, so I think this is best left alone.