Make fstest work out-of-the-box on Solaris:

• Solaris' setgroups(2) doesn't change process' effective gid, so set it explicitly.
• POSIX doesn't define O_NOFOLLOW. FreeBSD returns EMLINK when target is a symbolic link, but Solaris returns ELOOP then.
• Solaris doesn't define O_SHLOCK and O_EXLOCK flags.

Approved by: re (rwatson)