tests: portability fixes

tests: portability fixes

* tests/stat.test: dd obs= is not portable, use bs= instead.
* tests/stat32-v.test: Likewise.
* tests/stat64-v.test: Likewise.
* tests/net.test: Use $* instead of $@ in the quoted string.
* tests/net-fd.test: Likewise.
* tests/statfs.test: Quote { and } in regexps.
* tests/caps.awk: Likewise.
* tests/getdents.awk: Likewise.
* tests/net-yy-accept.awk: Likewise.
* tests/net-yy-connect.awk: Likewise.
* tests/sigaction.awk: Likewise.
* tests/unix-yy-accept.awk: Likewise.
* tests/unix-yy-connect.awk: Likewise.