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.

https://github.com/hanwen/go-fuse/blob/934a183ed91446d218b5471c4df9f93db039f6e1/fuse/mount_linux.go#L225-L232

References:

• https://github.com/libfuse/libfuse/issues/670
• https://github.com/AppImage/AppImageKit/issues/877
• https://github.com/probonopd/static-appimage/issues/4