Fix expectations for testcases per bsdgrep vs gnu grep from base/ports

The following failures occur with various versions of grep:

BSD grep:

• :context
• :context2

GNU grep (base):

• :color
• :oflag_zerolen

GNU grep (ports):

• :recurse_symlink

Tested with: bsdgrep (^/head@r316542), gnu grep (base/2.5.1), gnu grep (ports/2.27)
Reported by: Jenkins (bsdgrep failures)
Sponsored by: Dell EMC Isilon