Update regex in PluginService

This MR updates the regex in PluginService to use a lookahead as done for the regex in GaudiKernel/src/Lib/Platform/SystemLinux.cpp

@clemenci, as discussed here is this minor MR :)

changed the description

• [2017-11-15 13:38] Validation started with lhcb-gaudi-merge#304
• [2017-11-16 00:02] Validation started with lhcb-gaudi-head#1660
• [2017-11-16 00:02] Validation started with lhcb-future#603
• [2017-11-16 00:03] Validation started with lhcb-future-clang#377

changed milestone to %v30r0

added C++ framework label

added backport to v29 label

approved this merge request

merged

mentioned in commit 876ab8a7

mentioned in commit 6da3e1c7

mentioned in merge request !558 (merged)

removed backport to v29 label

mentioned in commit 5fe5f53a

mentioned in commit 2fd25b6f